Mocha cake

Put the coffee in a small cafetière with 250ml boiling water and set aside to brew. Preheat the oven to 200°C, gas mark 6. Grease and line a deep 23cm cake tin with baking parchment. Put the butter and 120g chocolate drops in a heatproof bowl and set over a pan of barely simmering water until melted. Mix in 100ml of the brewed coffee (strained). Put the flour, bicarbonate of soda, cocoa, soft brown sugar and a pinch of salt into a large bowl. Mix the yogurt and eggs in a jug, then use a balloon whisk to mix this into the dry mixture. Add the chocolate mixture and fold through.

Pour into the tin and bake for 45-50 minutes until a skewer inserted into the centre comes out clean. Leave in the tin for 10 minutes, then turn out onto a wire rack to cool completely.

To make the chocolate shards, melt the remaining chocolate in a small heatproof bowl set over a pan of barely simmering water. Spoon into a thick layer on a sheet of baking parchment and sprinkle with sea salt. Put in the fridge to harden.

For the buttercream, use electric beaters or a freestanding mixer to beat the butter, icing sugar and remaining brewed coffee (about 1 tbsp) until light. When the cake is fully cool, use a bread knife to carefully slice it in half horizontally. Spread half the buttercream over one layer, then top with the other layer and spread the remaining icing on top. Break the chilled chocolate into shards and arrange on the cake to finish.