For The Buttercream
MAKE THE CAKE BATTER
Preheat an oven to 175 degrees C. Whisk or beat the softened butter and sugar together until pale and fluffy. Separate the eggs, whisking the yolks into the butter mixture and placing the whites into a clean bowl. Loosen the mixture with the milk, then fold in the flour, baking powder and E&O Matcha powder.
WHISK THE EGG WHITES
Whisk the egg whites to soft peaks with a clean whisk, then fold into the cake mixture in two batches. (The first will be quite stiff, the second you'll be able to fold in carefully.)
BAKE THE SPONGES
Pour into a 24cm lined cake and shake the pan to level the mixture. Bake for 45 minutes, or until a skewer comes out clean when inserted into the middle. Allow to cool as you repeat with a second cake. Slice each cake into 2 discs using a serrated knife.
START THE BUTTERCREAM
Whisk the egg whites and caster sugar gently together in a bowl over a pan of simmering water until the sugar is warm enough to dissolve. Test by checking the mixture isn't at all grainy between your fingers.
FINISH THE BUTTERCREAM
Remove from the heat and whisk vigorously to form stiff peaks. Add the small knobs of room temperature butter into the egg whites as you whisk. Melt the white chocolate in a microwave, then whisk into the buttercream.
Leave to cool to room temperature to use. Layer sponge and buttercream alternately, then finish with a thin coating of buttercream all over. Place in a fridge to chill for an hour.
Add more buttercream to the top and sides, then smooth the top as much as possible. Use the end of a palette knife to create blobs around the cake and dust matcha powder over the top of the cake, using a doily s a stencil. Serves loads!