Make the Batter: In a large bowl, aggressively whisk the eggs, cold dashi stock, and soy sauce. Sift in the flour and baking powder, whisking until a very thin, watery batter forms. (The thinness creates the molten center).

Heat the Pan: Heat a specialized Takoyaki pan over medium-high heat. Use a brush or folded paper towel to generously oil every single spherical mold and the flat surface around them.

Pour and Fill: Pour the batter generously over the pan, completely filling the holes and overflowing onto the flat areas. Immediately drop one piece of octopus into each hole. Scatter the Tenkasu (tempura scraps) and green onions completely over the entire pan.

Form the Balls: Once the bottom of the batter sets slightly, use a Takoyaki pick or a bamboo skewer to trace around each hole, pushing the overflow batter down into the mold. Give each ball a 90-degree turn to let the raw batter flow into the bottom. Keep turning them repeatedly until they form perfect, round, golden-brown balls.

Garnish and Serve: Transfer the hot Takoyaki to a boat or plate. Slather them heavily with thick Takoyaki sauce and a zigzag of Japanese mayonnaise. Top with dancing bonito flakes and serve immediately (but be careful, the inside is lava-hot!).