In a large bowl, whisk together the flour, dashi (or water), and a pinch of salt until smooth. Add the eggs and whisk again until the mixture is fully combined. The batter should have the consistency of heavy cream. Let it rest for 15 minutes at room temperature.

Finely shred the cabbage into delicate ribbons. In a large mixing bowl, combine the shredded cabbage with the prepared batter. Use just enough batter to coat the cabbage - the vegetable should dominate, not the batter. Add the tenkasu, chopped pickled ginger, and sliced green onions. Gently fold everything together.

Heat a large skillet or griddle over medium heat. Add a generous amount of vegetable oil - okonomiyaki needs fat to develop that beautiful golden crust.

Pour half of the cabbage mixture onto the hot surface and shape it into a circle about 1 inch thick (2cm) and 6-8 inches in diameter (15-20cm). Don't compress the mixture; leave air pockets for a fluffy texture. If using pork belly, lay the slices across the top surface of the pancake.

Cook undisturbed for 5-6 minutes. The pancake is ready to flip when the edges turn golden brown and the surface begins to set. The bottom should be deeply golden and crispy.

Using one or two large spatulas, carefully but firmly flip the pancake. If you're nervous, use two spatulas for extra security. Cook the second side for another 5-6 minutes until deeply browned and cooked through.

Transfer your okonomiyaki to a plate. While it's still hot, paint the entire surface generously with okonomiyaki sauce. Drizzle Japanese mayonnaise in zigzag patterns across the top. Sprinkle with aonori and finish with katsuobushi flakes, which will dance from the residual heat.

Serve your okonomiyaki piping hot, optionally accompanied by a light green salad or tsukemono (Japanese pickled vegetables). Repeat the process with the remaining mixture for the second pancake.