Separate eggs. Beat egg whites and 3 tbsp. cold water until stiff. Finally pour in sugar. Beat the egg yolks separately. Mix 150 g flour and starch, sieve onto the egg foam and fold in carefully. Mix the frozen blueberries with 1 tbsp. flour, carefully fold into the sponge cake mixture and place in a greased, flour-sprinkled ring cake mould (2.5 litres capacity; 22 cm Ø). Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 45 minutes (test with sticks)
Take the cake out of the oven. After about 10 minutes, carefully turn out of the tin and let it cool down on a cake rack. Whip butter with icing sugar until white-creamy. Colour blue with food colouring. Spread the cake loosely with the butter cream and sprinkle with coconut flakes. Chill for about 15 minutes and then serve
waiting time approx. 2 hours