Instructions

For the cake

1. Preheat the oven to 180°C/350°F (without fan).
2. Grease and line the base of two 20 cm (8 inch) cake tins.
3. Dissolve the instant coffee powder in the boiling water. If you want a strongly coffee-flavoured cake, I suggest using 4 teaspoons.
4. Place the walnuts and caster sugar into the bowl of a food processor and blitz until you have a fine powder.
5. Add the butter, flour, coffee mixture, baking powder, baking soda, and eggs.
6. Blitz again until you have a smooth batter.
7. With the motor still running, pour a little bit of milk down the funnel until the batter is a soft, spreadable consistency.
8. Divide the batter between both cake tins.
9. Bake for about 25 minutes, or until the cakes are lightly golden and a cake skewer inserted in the centre comes out clean.
10. Cool the cakes in their tin on a wire rack for about 10 minutes before inverting onto a wire rack. Remove the cake tins and baking paper from the cake.
11. Leave the cakes to cool completely.

For the frosting

1. Dissolve the instant espresso powder in the boiling water
2. Using a stand mixer with the flat paddle attachment, beat together the icing sugar (powdered sugar), butter and coffee mixture until you have a thick and spreadable frosting.

To assemble the cake

1. Place one sponge upside down on a plate or cake platter.
2. Spread half of the frosting onto the sponge and spread it evenly.
3. Place the second sponge on top.
4. Cover the top sponge with the remaining frosting.
5. Decorate the cake with walnut halves.