In a large mixing bowl, combine the flour, dashi stock, and a pinch of salt and pepper. Whisk until smooth.
Fold in the shredded cabbage, green onions, and cooked pork belly or shrimp if using. Mix until well combined.
Heat a non-stick skillet over medium heat and add the vegetable oil.
Pour half of the batter into the skillet, spreading it into a round pancake shape about 1 inch thick.
Cook for about 4-5 minutes on one side until golden brown, then carefully flip and cook for another 4-5 minutes on the other side.
Repeat with the remaining batter to make a second pancake.
Once cooked, transfer the pancakes to a plate. Drizzle with mayonnaise and okonomiyaki sauce.
Top with bonito flakes and aonori if desired. Serve hot.