As far as possible, the batter of the tempura should be very cold, in order to create the maximum contrast with the frying oil and enhance the crunchiness. In the ten-don recipe we used a egg-free batter, in this case we propose instead one that involves the use of an egg.
For an entirely gluten-free version, you can use rice flour, but you have to be very careful because the batter will be less dense. If you want to go this way, you need to use less water and make sure that the egg + water mixture reaches a total weight of 200g. To this must be added to 80g of rice flour. Unlike normal batter, this needs to be well mixed often because rice flour tends to settle on the bottom.