Grease and base line 2 x 20cm cake tins. Preheat the oven to 175C
1. Cream together the butter and sugar until andit is pale and fluffy then beat in the eggs, one at a time. If the mixture begins to separate (curdle), add a tablespoon of flour, taken from your weighed amount, which will help to stabilise the mixture.
2. Sift together the flour and baking powder then using a metal spoon or spatula in a cutting action, fold in the flour to the butter mixture followed by the ground hazelnuts followed by lemon zest and finally both the espresso grinds and liquid coffee.
3. Place half of the mixture into each of the prepared tins smoothing out with a knife. Bake for about 25 - 30minutes until the cake is golden and springs back when you gently touch the surface. Allow to stand in the tin for about 30 minutes and then turn out onto a cooling rack.
When completely cold, fill and top with mascarpone cheese, sprinkle with ground espresso coffee and decorate with chocolate coffee beans.