Deep-fried Horse Mackerel (Aji Fry) is a traditional Japanese home-cooking dish, and one of my favourite dishes. Butterflied horse mackerel (also called yellowtail or jack mackerel in Australia) is coated in breadcrumbs and deep-fried to a perfect golden colour. Nothing is better than biting into the hot deep-fried crumbed fish!
Horse mackerel is reasonably cheap in Australia, like sardines. It is sometimes even cheaper than sardines. But in Japan, horse mackerel is usually more expensive than sardines, particularly the fatty large ones. Just after migrating to Australia, I learnt that horse mackerel was used as a fishing bait in Australia. I could not believe it.
In the early 1980s when I was working at a life insurance company, I told one of my colleagues that I caught a quite few horse mackerels from the ocean and made sashimi out of them. My colleague had a fit because he only knew horse mackerel as fishing bait. I had to educate him about this fish, but I don’t think he wanted to know about it.
About Aji Fry
Horse mackerel is called ‘aji’ (鯵) in Japanese. It is actually the same phonetic spelling as the Japanese word for taste ‘aji’ (味), but the intonations are different. You need to put the accent on ‘a’ when you pronounce it as fish. On the other hand, ‘aji’ as taste does not have a strong accent on either of the syllables.
It is said that the reason why this fish is called Aji is because it has a good ‘aji’ (taste). I have to agree with that.
Aji Fry (鯵フライ) is classified as yōshoku (Western-style food). In the early Meiji period, the Western-style fried crumbed dishes such as cutlets and croquets were introduced along with breadcrumbs. At the time, they were shallow-fried, just like how we cook cutlets even now.
The Japanese counterpart of the cutlet is Tempura, but it uses a large amount of oil and deep-fry battered food. So, instead of shallow-frying crumbed food, the new cooking method of deep-frying crumbed food, ‘fry ryōri’ (フライ料理) was established in Japan.
Crumbed meat and croquets were all deep-fried and served as Japanese yōshoku. The ingredients were extended to seafood, but horse mackerel did not get attention from the high-end restaurants. They mainly served deep-fried crumbed prawns and oysters, perhaps because horse mackerel was not considered to be suitable for fancy restaurants. In fact, horse mackerel was widely consumed by common people.
Aji Fry became popular only after WWII, when Japan could produce its own breadcrumbs and sell to the public. It was also served at school meal. Although Aji Fry started as a yōshoku dish, it has almost transformed into washoku (Japanese cuisine) nowadays. According to a survey conducted in 2018, Aji Fry ranked 3rd as the best dish for a bento box.
What’s in my Deep-fried Horse Mackerel (Aji Fry)
- Butterflied horse mackerels
- Salt and pepper
- Beaten egg
- Panko breadcrumbs
- Oil to deep-fry
- Shredded lettuce for serving
- Tonkatsu sauce for serving (I used Bull-Dog sauce)
The size of a whole horse mackerel can vary but I would recommend a medium-sized fish. My fish was 20-22cm / around 8¼” from head to tail (120-140g / 4.2-4.9oz). After removing the head and the bones, the weight of the fillet is almost halved.
I used the store-bought Bull-Dog Tonkatsu sauce. Chūnō sauce is good too. If you don’t have it, you can mix Worcestershire sauce and tomato ketchup as an alternative, or just serve Worcestershire sauce. Incidentally, some people eat Aji Fry with soy sauce.
How to Make Aji Fry
The traditional Aji Fry uses a butterflied whole fish, without the head. There is a particular way of butterflying horse mackerel for Aji Fry, and this is the most time-consuming part of making today’s dish. So, I have explained the method with a video in the next section.
Once you have butterflied the fish, the rest is the same as deep-frying any crumbed fish or meat.
- Remove scales and butterfly the horse mackerel.
- Coat the horse mackerel with flour, egg, then panko breadcrumbs.
- Deep-fry for a couple of minutes.
Aji Fry can be frozen for up to 1 month. It is best to freeze them before deep-frying. Thaw in the fridge overnight, then deep-fry.
How to Butterfly Horse mackerel for Aji Fry
There are two ways of butterflying fish – (1) cut along the belly side to open the fish and (2) cut along the dorsal side to open. The former is called ‘harabiraki’ (腹開き) in Japanese and the latter is called ’sebiraki’ (背開き). The word ‘hara’ (腹) means belly and ‘se’ (背) means back. The word ‘biraki’ (開き) is the noun form of the word ‘hiraku’, which means open. The sound of the first syllable is changed for easier pronunciation.
Sebiraki method vs Harabiraki method
In the case of Aji Fry, you use the sebiraki method so that the thinnest part of the fish, i.e. the belly part, is in the centre and the fleshiest part is on the outside edge.
There are a couple of reasons for that:
- When you take the first bite, you get the fleshy portion of the Aji Fry, which gives you a better food experience.
- If the thin belly sections are on the edges (the harabiraki method), the edges tend to curl up when the butterflied fish is deep-fried.
The harabiraki method is probably more commonly used not only in Japanese cuisine but also in Western cuisines. It is more natural to open the belly and remove guts first, then butterfly. It is also easier.
Step-by-step Sebiraki Method
Firstly, you will need a very sharp knife. The major steps are listed here but the video below shows how to butterfly in more detail.
- Remove the scales and cut the head off.
- Remove the guts and clean without breaking the belly skin.
- Starting from the dorsal side, detach one side of the fillet from the backbones, keeping the belly skin intact.
- Do the same on the other side of the fillet. Cut the backbone off.
- Remove the rib bones in the centre of the butterflied fish, then remove pin bones from the fillet.
Watch How to Butterfly Horse Mackerel for Aji Fry
The recipe card contains very detailed steps of how to butterfly a fish that correspond to the video. I also attached the step-by-step photo with the instruction numbers.
If this is too difficult for you, you can make two fillets out of a horse mackerel and make two pieces of Aji Fry. The appearance is not the same as the traditional Aji Fry, but it will still be tasty.
Fish Bone Senbei (Fish Bone Chips)
Whenever you make fillets out of small/medium fish, be it horse mackerel or whiting as in my post Semi Dried Whiting Fillets, you will be left with back bones with flesh stuck on them. The flesh between the bones is very tasty, so don’t throw them away. I always make Fish Bone Senbei from them by deep-frying the bones until they become crunchy and golden brown. They are perfect for nibbles and are full of calcium.
Here is how to make Fish Bone Senbei:
- Sprinkle a pinch of salt over the fish bones, or a small amount of soy sauce to give a light salty flavour to the bones.
- Leave them for few minutes, then pat-dry the bones. No coating with flour or corn flour.
- Deep-fry at 170°C / 338°F for about 8-10 minutes.
Bones are not chewy but crunchy. They are so good!
Deep-fried Horse Mackerel (Aji Fry) is a traditional Japanese home-cooking dish. Butterflied horse mackerel is coated in breadcrumbs and deep-fried to a perfect golden colour.
The method of butterflying the fish is unique as it opens the fish from the dorsal side instead of the belly side. This method is called ‘sebiraki’ in Japanese and the very detailed instruction for butterflying a fish is included in this recipe.
Don't forget to see the section 'MEAL IDEAS' below the recipe card! It gives you a list of dishes that I have already posted and this recipe that can make up a complete meal. I hope it is of help to you.
- 4 horse mackerels (whole, medium size, note 1)
- ¼ tsp salt
- ¼ tsp pepper
- 1½ tbsp flour
- 1 egg beaten
- 1½ cup panko breadcrumbs
- Oil for deep-frying
- Shredded lettuce
- Tonkatsu sauce (or other sauce such as Worcestershire sauce, note 2)
Remove the scales on both sides of the fish by sliding the tip of the knife from the tail end towards the head.
Place the knife where the tail begins, facing the blade to the head. Move the knife at a very low angle towards the head and trim the bony scales (scutes) along the lateral line, which ends close to half-way.
Remove the head by cutting at a slight angle behind the gill and the front fin.
Using a finger or a narrow knife, remove the guts from the opening, without breaking the thin flesh around the belly.
Rinse the fish and clean the cavity in the belly. Pat dry, including inside the cavity.
Starting from the head of the fish, make a shallow incision on the dorsal side all the way to the tail. The incision needs to be on your side of the back bones.
Using the tip of the knife, extend the incision towards the belly along the backbones. It is easier if you lift the flesh that is already removed from the bones so that you can see where your knife is cutting.
Detach the rib cage by cutting the rib bones along the back bones.
Continue to remove the flesh along the back bones until you reach to the belly, but keep the belly skin intact. You now have a butterflied fish with the bone in.
Flip the butterflied fish over (skin side up) and make an incision on the other side of the dorsal in the same way.
Chop the backbone at the tail end, keeping the tail attached to the flesh (note 4).
Now you have a butterflied fish fillet. If small pieces of guts are left on the belly, wipe them off using kitchen paper.
Place the tip of the knife where the rib bones start and trim the flesh with the rib bones very thinly. Do the same on the other side of the rib bones.
There is a very sharp hard thorn in front of the anal fin. You need to remove it. I used kitchen scissors for this.
The last step is to remove the pin bones from the fillet. Run your finger along where the backbone was and feel the bones to locate them. Remove all of them using a pair of fish bone tweezers or pliers.
Sprinkle salt and pepper over both sides of butterflied fish fillets.
Working one fillet at a time, coat a fillet with flour, then pat to shake off excess flour. Place it in the egg and coat all over. Allow excess egg to drip, then transfer to the breadcrumbs.
Cover the entire fish with breadcrumbs, and gently press down so that a good layer of breadcrumbs is stuck on both sides. Repeat for the rest of the fillets.
Heat oil in a frying pan to 170°C / 338°F. The oil should be about 3cm / 1¼” deep.
Gently place the crumbed fish skin side up. Do not crowd the oil with too many fish pieces (note 5). Cook for about 1-1½ minutes, then turn the fish over. Cook for further 1 minutes or so, until golden brown (note 6).
Transfer the fried fish to a tray lined with kitchen paper to drain excess oil.
Place two Aji Fry pieces with shredded lettuce on each serving plate. Serve immediately with the sauce of your choice.
1. Also called yellowtail and jack mackerel in Australia.
My fish was 20-22cm / around 8¼” from head to tail (120-140g / 4.2-4.9oz). The size of the fish can be smaller or larger. But for ease of handling, I don’t recommend using too small or too large fish.
2. I used Bull-Dog Tonkatsu sauce as the thick fruity sauce goes well with the crumbed fish. By mixing Worcestershire sauce and tomato ketchup, you can make a similar sauce.
You can of course use Worcestershire sauce or other sauces.
3. You will need a very sharp knife for this. Please also see the video in the post, which shows how to butterfly a fish using the sebiraki method (opening from the dorsal side).
If you find it too hard to make a butterflied fish, you can cut two fillets out of each fish instead. The appearance is not quite the same as the traditional Aji Fry, but it’s still delicious.
4. Do not discard the back bones with flesh on them. You can make crunchy Fish Bone Senbei out of them. Please see the last section in the post for how to make it.
5. I fried two fillets at a time.
6. If your fish is smaller/larger, the frying time needs to be slightly shorter/longer respectively.
7. Aji Fry can be frozen for up to 1 month. It is best to freeze them before deep-frying. Thaw in the fridge overnight, then deep-fry.
8. Nutrition per serving. It is assumed that the oil absorption rate is 20% of the weight of the fish fillet.
serving: 280g calories: 847kcal fat: 46g (71%) saturated fat: 6.7g (34%) trans fat: 0.2g polyunsaturated fat: 9.7g monounsaturated fat: 26g cholesterol: 159mg (53%) sodium: 749mg (31%) potassium: 772mg (22%) carbohydrates: 63g (21%) dietary fibre: 3.9g (16%) sugar: 5.1g protein: 43g vitamin a: 5% vitamin c: 4.7% calcium: 15% iron: 35%