Japan's fish-shaped street snack - a thin, crisp waffle shell filled with warm sweet red bean paste. The batter should be mixed just until smooth, since overmixing makes the shell tough instead of light.
1.Sift the flour and baking powder into a bowl and make a well in the center.
2.In a separate bowl, beat the egg lightly, then whisk in the milk, water, sugar, and salt.
3.Pour the wet ingredients into the well of flour and mix just until smooth, being careful not to overmix, which would make the taiyaki tough instead of light.
4.Cover and refrigerate the batter for at least 30 minutes to rest.
5.Divide the red bean paste into portions and shape each into a small log to fit inside the mold.
6.Heat a taiyaki pan over low heat and grease both sides of the mold, then fill one side halfway with batter.
7.Place a portion of red bean paste on top of the batter, then cover with a bit more batter, close the pan, and cook, flipping periodically, for 10-15 minutes until both sides are deep golden brown.
8.Serve warm, when the shell is crispiest and the filling is still molten.