Mix ½ tbsp oyster sauce, ½ tbsp Japanese soy sauce (koikuchi shoyu), 1 tsp Worcestershire sauce, ½ tsp tomato ketchup, ¼ tsp sake, ¼ tsp sugar, 1 pinch ground black pepper and ½ tsp toasted sesame oil in a small bowl to make the yakisoba sauce.
Heat a frying pan on medium-high and once hot, add 1 ½ tsp cooking oil and 1 portion yakisoba noodles. Fry undisturbed until crispy underneath, then flip and repeat.
Pour the yakisoba sauce over the noodles and stir fry until they're evenly coated. Remove from the stove and set aside for later.
Take a large frying pan and heat on medium-low. Spread 1 ½ tsp cooking oil around the pan and wipe away the excess with kitchen paper so that only a thin film remains.
While the pan is heating up, make the crepe batter by whisking the 30 g all-purpose flour, 60 ml dashi stock, 1 pinch white sugar and 1 dash mirin in a small jug until smooth.
Briefly lift the pan off the heat and pour 3/4 of the mixture into the center of the pan. Spread it out thin using the back of a spoon, then place the pan back down and sprinkle 1 tbsp bonito flakes (katsuobushi) over the wet batter.
Add 50 g green cabbage, 4 tbsp fried squid snack (ikaten) and 50 g bean sprouts one layer at a time, then drizzle the leftover batter over the top to act as a glue between the layers.
Lay the 100 g thinly sliced pork belly over the top and cover the pan with a lid. Steam-fry for 5 minutes.
While you wait, mix ½ tbsp Worcestershire sauce, ½ tbsp oyster sauce, 1 tbsp tomato ketchup, ½ tbsp honey and ½ tsp Japanese soy sauce (koikuchi shoyu) in a small bowl to make your okonomiyaki sauce. Set aside for later.
Remove the lid, flip the okonomiyaki and cover with the lid once more. Cook the other side for 5 minutes or until the pork is cooked through. Slide the contents of the pan onto a large plate.
Crack 1 egg into a separate bowl with 1 pinch salt and whisk until the yolk and white are combined.
Use kitchen paper to wipe the pan clean, then add a drizzle of oil and spread it around using kitchen paper to remove any excess. Pour the whisked egg into the pan and swirl it around to evenly coat the bottom of the pan.
Once it's about 80% cooked, place the cooked yakisoba on top and lightly press it down. Place other half of the okonomiyaki on top so the crepe is on top and the pork is sandwiched in the middle.
Use a spatula to peel the edges of the egg and loosen it from the pan and carefully flip the whole thing onto a plate. The egg layer should be on top, the crepe on the bottom.
Generously coat with the homemade okonomi sauce, 1 tbsp finely chopped green onions and an 1 pasteurized egg yolk (optional). Enjoy!
Notes
Stop pouring the crepe before it thickens: Aim for a narrow window. Too thick and it cooks up rubbery and dense, too thin and it tears the moment cabbage lands on it. Use most of the batter but spread it wide and stop while the surface still looks barely translucent.Spread the crepe in a single pass: Pour into the center and push outward with the back of a spoon, never going over the same spot twice. A second swipe drags and tears the setting batter. If a hole opens, dab batter on and let it set.Use a bigger pan if you flip it yourself: A pan that barely fits leaves no landing room for the turn.Commit to a freehand flip and go fast: If you flip it by hand, turn it in a single quick decisive motion. The instinct to ease a nervous stack over slowly is exactly what drops it mid-air. Decide, then go, or skip the risk with the plate invert.