Step 1

Preheat the oven to 180°c/fan160°c/gas Grease and base line 2 x 20cm sandwich tins with butter and baking paper.

Step 2

Beat the butter in a bowl with an electric hand whisk until soft and creamy. Add the caster sugar and beat until light and fluffy, then beat in the eggs, 1 at a time, adding a small spoonful of flour with the second and last egg, to prevent curdling. Beat in the coffee, then sift over the remaining flour and baking powder and fold in, followed by the chopped walnuts.

Step 3

Divide the cake mixture equally between the prepared tins and lightly level the tops. Bake in the centre of the oven for about 30 minutes, until well risen and golden and the tops spring back when lightly pressed with a fingertip. Leave the cakes to cool in the tins for 10 minutes, then turn out onto a wire rack and cool.

Step 4

Make the tiramisu cream. Put the mascarpone into a mixing bowl and gradually beat in the double cream, followed by the coffee liqueur, caster sugar and vanilla extract.

Step 5

Place 1 cake, flatter-side up on a serving plate and spread with half of the tiramisu cream. Cover with the second cake, flatter-side down and spread the top with the rest of the tiramisu cream. Mix the cocoa with the icing sugar and dust over the cake. Decorate the top of the cake with the walnut halves.