Heat the oven to 160C/140C fan/gas 3. Butter 3 x 18cm cake tins and line with baking paper.
Make the sponge first. Mix the flours, desiccated coconut and baking powder in a bowl with 1/8 tsp salt. Whisk the coconut milk, egg whites, milk and coconut extract in another bowl. Beat the butter and sugar until pale and fluffy. Add the dry and wet ingredients and whisk until smooth.Divide the mixture between the tins, level, then bake for 35-40 minutes. Cool in the tins for 5 minutes, then turn onto wire racks to cool completely.
To make the frosting, put the egg whites in a stand mixer with the whisk attachment, or a big, clean bowl with an electric whisk. Mix 200g sugar and 4 tbsp of water in a small pan and heat gently until the sugar dissolves and makes a syrup.
Whisk the whites until firm, add the remaining 75g caster sugar and whisk to stiff peaks.
Boil the syrup until it reaches 120C on a sugar thermometer. While whisking the meringue on the highest speed, slowly pour in the syrup so it hits the meringue, not the bowl. Keep whisking until the meringue is room temperature.
Whisk in a spoonful of butter at a time, slowly but steadily, till you have a shiny, smooth meringue icing. It’ll probably be a little thin, and at this stage it might look greasy and split. If this happens, put it in the fridge to firm for 15-20 minutes, then whisk again and it’ll come back together to a smooth, thick buttercream.
To finish, use the buttercream to fill and cover the cake. Press the coconut chips onto the icing and decorate with truffles.
175g unsalted butter
275g plain flour
50g desiccated coconut
1 tablespoon baking powder
200ml light coconut milk (whisked smooth)
200ml egg whites (about 5 large)
1tablespoon coconut extract
400g white caster sugar
2 egg whites
275g white caster sugar
350g unsalted butter
125g coconut chips or flakes
5 white chocolate truffles