Sift cake flour, baking powder, and baking soda into a large bowl.

Add sugar and whisk well to combine.

In a medium bowl, whisk the egg and then add whole milk. Combine well.

Pour the wet ingredients into the dry ingredients and whisk well. Refrigerate the batter for at least one hour to rest.

Pour the batter into a measuring cup or jug to ensure you have about 1? cups.

Preheat the taiyaki maker over medium-low heat and grease the pan with some neutral oil.

Fill the taiyaki pan mold about 60% full of batter.

In the center of each mold, put about 1 Tbsp of sweet red bean paste and pour more batter on top to cover it.

Close the lid and immediately flip.

Cook for 2 to 2? minutes on that side. Then flip and cook for another 2 to 2? minutes. Check if the taiyaki is golden brown, then remove from the pan and cool on a wire rack.

Continue cooking the remaining taiyaki.

Serve warm. If the taiyaki get cold, you can toast them in the toaster oven or oven until they?re crispy on the outside.