Make the takoyaki sauce before you start cooking so that it is ready to be drizzled once the takoyaki is done.
Have all the ingredients for the filling ready before mixing the batter.
To make the batter, simply stir all the ingredients together. To make pouring easier and less messy, pour the batter into a container with a spout.
Heat the takoyaki pan and moisten each mold with cooking oil.
When the oil begins to sizzle, fill the molds with batter. It is quite okay if the batter overflows from the molds a little.
Scatter chopped octopus, scallions, pickled red ginger and tempura scraps directly on the batter.
Let the batter cook for a few minutes to firm up the bottom.
Using bamboo skewers (or use chopsticks), cut through the batter (where it has overflowed) to separate the still unformed balls.
Carefully lift the wet balls and turn slightly (do not flip to invert!). As you turn, gather the excess batter around each mold and tuck in.
Repeat the turning process every minute or so to brown every inch of the surface of the balls.
The takoyaki is done when the balls are uniformly browned.
Transfer the takoyaki to a plate. Drizzle the sauce and Japanese mayo over the balls. Sprinkle with aonori and bonito flakes, and serve while very hot.