Ingredients

· 100 g walnuts

· 140 g golden caster sugar

· 3 tablespoons milk

· 2 teaspoons coffee granules

· 100 g salted butter

· 2 tablespoons walnut oil

· 2 eggs

· 75 g flour

· 75 g wholemeal flour

· ½ teaspoon bicarbonate of soda

· 350 g unsalted butter

· 400 g icing sugar

· 2 tablespoons cocoa powder

· 2 tablespoons coffee granules

· 1 teaspoon vanilla extract

Method

Heat the oven to 180°C. Line a 12-hole muffin tin with muffin cases. Put the walnuts in a food processor with about half the sugar and whizz until very finely chopped. Mix the milk in the coffee and dissolve it. Tip the walnut-sugar mix, remaining sugar, milky coffee, soft butter, oil, eggs, flours and bicarb into a mixing bowl and beat with an electric whisk until smooth. Divide between the cases then bake for 18 minutes, or until golden and risen, and a skewer poked into the centre comes out clean. Lift the cakes onto a wire rack to cool completely. For the icing, put the butter in a mixing bowl and beat for about five minutes until very pale and creamy. Sift in the icing sugar and cocoa then add the coffee and vanilla and beat for another five minutes until very fluffy. Pipe swirls of icing on top of each cake, then leave to set for 20 minutes before serving.