Prepare the dashi: Bring 1 cup water with a dashi packet to a boil in a saucepan. Simmer for 2-3 minutes, then remove from heat and measure out 3/4 cup of the strained dashi.
2
Combine dry ingredients: In a large bowl, whisk together 1 cup flour, 1/4 tsp salt, 1/4 tsp sugar, and 1/4 tsp baking powder.
3
Add the dashi and grated nagaimo to the dry mixture and stir well to combine. Set aside the batter base.
4
Prepare the cabbage: Cut the cabbage into thin slices, then chop into small 1/4-inch pieces, wash thoroughly, and drain well to remove excess moisture.
5
Prepare the pork: Cut the pork belly slices into approximately 4-inch pieces.
6
Make the batter: Add 4 large eggs to the rested batter base, then add 1/2 cup tempura scraps and pickled red ginger. Mix until combined.
7
Fold in the cabbage: Add the chopped cabbage in thirds to the batter, mixing well after each addition to ensure even coating.
8
Make the okonomiyaki sauce: Combine 1/2 cup ketchup, 1/4 cup oyster sauce, 3 tbsp sugar, and 7 tbsp Worcestershire sauce in a measuring cup. Mix until the sugar dissolves completely.
9
Heat the pan: Place a pan over medium heat and spray oil evenly across the surface.
10
Cook the okonomiyaki: Pour the batter into the hot pan and shape into a 6-inch circle. Place 3 pork belly slices on top. Cover and cook on medium-low heat for 5 minutes.
11
Flip: Carefully flip the okonomiyaki, cover, and cook for another 5 minutes on medium-low heat.
12
Final cooking: Flip one last time and cook uncovered for 2 minutes.
13
Serve and garnish: Transfer the okonomiyaki to a plate, spread the sauce on top with a spoon, drizzle Japanese mayo in a zigzag pattern, drag a chopstick through the mayo to create a decorative pattern, then sprinkle with bonito flakes, seaweed powder, chopped green onions, and pickled red ginger.