Form the mixture: Mix the kuzu arrowroot starch and the shiratamako rice flour and 100ml of water in a bowl. Mix until a paste forms. Add the remaining 100ml of water and sift the flour and sugar into the bowl. Mix until combined. Set aside approximately 3-4 tbsp of the finished mixture to be used for the topping.
Wet the mould: Place some water in a small rectangular mould, about 6 in x 5 in, and pour the water out. A little wetness will help the cake come out easier.
Place into mould: Next, place the mixture into the mould and steam in a steamer for about 20 min. To ensure that water does not fall on top of the cake while steaming, place a tea towel under the lid of the steamer. When finished, remove from the steamer, and gently remove any wetness from the top of the cake with some kitchen roll. This will help the next layer stick to the base.
Spread the mixture: Evenly spread the drained azuki beans over the top of the cake and add the reserved 3-4 tbsp of the cake mixture on top. Spread the mixture so it covers the entire surface.
Steam: Now, place the cake into the steamer again and steam for a further 10 min. Remove from the steamer, and allow to cool in the fridge.
Cut into squares: When cooled, cut into square pieces, and then cut each square into a triangle. Makes about 12 pieces.
