180g unsalted butter, softened, plus extra for greasing mould
200g self-raising flour, plus extra for dusting mould
50g hazelnuts, roasted and peeled
1 heaped tsp baking powder
200g castor sugar
4 eggs, separated
Pinch of salt
100g hazelnut meal
1 tsp vanilla extract
Grease and dust a 23-centimetre ring mould (with a hole in the middle). Roughly chop hazelnuts. Sift together flour and baking powder in one bowl. In another, beat together butter and sugar. In a small bowl, whisk together egg yolks with salt. Slowly add this to butter and sugar, mixing well. Mix in sifted flour and baking powder, then espresso, hazelnut meal and vanilla. Whisk egg whites until they form firm peaks and fold into the mixture. Pour mixture into greased and floured cake mould. Sprinkle chopped hazelnuts on top and bake in a preheated 180C oven for 45 minutes. Remove from oven and let cool for 5 minutes before turning out onto a cooling rack.
Once cooled completely it can be served with espresso custard, made by mixing 2 espresso shots with 250ml of custard.