Heat a takoyaki pan on the stove top. Keep the temperature on medium.
Pour a teaspoonful of the shell batter into each indentation. It is important to stir the batter before in the bowl each time you scoop out a teaspoonful to make sure that the solids do not settle at the bottom of the bowl.
Pour a teaspoonful of the custard filling on top of the shall batter. Again, it is the better practice to stir the custard filling in the bowl each time you take a teaspoonful to prevent the rice flour from settling at the bottom.
When the pancake is bubbly along the edges, add a pinch or two of your preferred topping.
When the edges of the pancakes are browned, take a skewer to tilt each pancake one by one and, with your other hand, use a spoon to scoop out the pancake and move it to a cooling rack.