In a big bowl, whisk flour and Dashi (fish broth) together until smooth. Stir egg and yam to flour mixture. Season it with salt and soy sauce.
Add chopped cabbage, onions, and ginger to the batter and mix.
Heat oil in a skillet, pour half of the pancake batter into an 8" circle, and lay 3 pieces of pork slices on it. Fry at medium heat until the bottom becomes golden brown, about 5-7 minutes.
Flip to fry the other side until the pork becomes crispy, about 5-7 minutes.
Flip one more time, pork side up, and spread Okonomiyaki sauce and mayo on the pancake.
Sprinkle dried green seaweed, then dried bonito flakes over the pancake. Serve hot.