2 tsp instant coffee, mixed with 100ml/3½fl oz boiling water, then cooled
25g walnut halves, chopped, plus 12 more for the tops
200ml tub mascarpone (you'll find this with the soft cheeses)
2 tbsp light muscovado sugar
Heat oven to 180C/fan 160C/gas 4 and make sure there’s a shelf ready in the middle. Line a 12-hole bun tin with fairy cake cases. Beat the butter, sugar, flour and eggs with 4 tsp of the coffee and a pinch of salt until creamy. Stir in the chopped walnuts.
Spoon the mix into the cases (start by adding 1 heaped tsp to each, then go back and top them up - that way they should all be of equal size), then bake for 18-20 mins until light golden and springy. Cool for a few mins in the tin, then lift the cakes out and cool completely on a rack.
Put the mascarpone, 3 tsp more of the coffee and the sugar into a large bowl, then beat together. Spread a dollop of the coffee cream onto the top of each cake, then finish with a walnut half. The cakes are best if they’re iced fairly near the time of eating, so if you’re making ahead, whip up the mascarpone mix, keep in the fridge, beat it again, then spoon onto the cakes just before serving. Un-iced cakes will keep up to 2 days in an airtight container.