To make the strong coffee, dissolve 2 teaspoons of instant coffee in 3 tablespoons of boiling water
Preheat the oven to 180C/Gas4; grease two 20cm sandwich tins and line the base with baking parchment
Cream the butter and sugar together, add the coffee and beat in the eggs little by little; sift the flour and baking powder together and fold in
Divide the mixture between the prepared tins and bake for 20-25 minutes until risen and the tops spring back when slightly pressed with a fingertip
Allow to cool in the tins for a few minutes then turn out, peel away the paper and cool on a wire rack
Make the butter cream by blending the butter, icing sugar and coffee together until smooth
Take one cake and arrange wooden skewers over the top to mark out eight portions; sieve icing sugar over the top and then remove the skewers; pipe on eight butter cream rosettes and top each with a walnut piece
Add the chopped walnuts to the remaining butter cream and spread over the second cake; put the first cake on top of this
8 servings