Cut the 150 g green cabbage into into small rough pieces.
Once the batter has been resting for 30 minutes, divide it into two bowls and place one of them back in the fridge for later. (Alternatively, make two at the same time in two frying pans.)
Preheat your pan on a medium/medium-high setting.
Once the pan is hot, add half of the cabbage, 1 tbsp tempura flakes, 1 tsp red pickled ginger and 1 egg to each bowl of the batter and mix well. (If you want to add other ingredients such as cheese, kimchi, mochi etc add them here. See in post for more ideas.)
Add the oil to the pan and swirl around until evenly coated. Pour the okonomiyaki mixture into the center of the pan and use a spatula to neaten up the edges.
Lay the slices of pork belly over the top of the wet mixture and fry the okonomiyaki until the bottom starts to become brown and crispy.
Carefully flip it over and place a lid on the pan. Reduce the heat to medium-low and continue to fry with the lid for about 5 minutes or until cooked all the way through.
Pierce the middle with a toothpick to make sure it's cooked. If the toothpick doesn't come out clean, continue to cook on a low heat and check it every few minutes until it's done.
Once it's cooked through, flip it over again and pour half of the sauce over the top. Use a pastry brush or spoon to spread it evenly. (You can do this while it's still in the pan or transfer it to a plate first.)
Drizzle with mayonnaise and sprinkle generously with bonito flakes and aonori.
Repeat the process again from step 4 with the remaining ingredients. (Tip: You can eat the first one while the second one is cooking.)
Enjoy!