Okonomiyaki: Japanese Cabbage Pancake

In a large bowl, whisk together egg and 1 cup dashi or water.  Add flour, baking powder, salt, and black pepper and whisk until combined.  Fold in cabbage and green onions with a large spoon.  In a large skillet over medium heat, heat 2 tablespoons of oil.  Scoop half of batter into skillet and spread into an even layer, about 1/4-inch thick.  Cook until golden on the bottom, about 3 minutes.   Lay half of pork belly evenly over the top.  Flip and lower heat to medium-low.  Do not press down on the pancake as it cooks.  Add more oil if the pan looks dry.  Cook until browned, about 3 minutes.  Transfer to a large plate, then repeat with remaining batter.  Make sauce: In a small bowl, whisk together ketchup, Worcestershire, honey, and salt.  Drizzle okonomiyaki with sauce and mayo.  Sprinkle with green onions, nori flakes, bonito flakes, and picked ginger.  Serve while hot.