Tiramisu ice cream

Bring ½ a kettle of water to the boil. In a shallow bowl, use a fork to mix the espresso powder, ½ tbsp cocoa, the sugar and 2 tbsp rum with 100ml just-boiled water; set aside. In a large bowl, use an electric hand mixer to beat the mascarpone and whipping cream to soft peaks (2-3 minutes). Gradually beat in the condensed milk, then the remaining 2 tbsp rum until the mixture reaches soft peaks again (2-3 minutes more).

Break each sponge finger into 3 bite-sized pieces. Dip each quickly into the coffee mixture (using a teaspoon is helpful), then transfer to the bowl with the cream mixture. Carefully fold the mixture together (along with any coffee liquid that is left in the bowl). Pour into a 900g tin or freezerproof container and securely cover with baking parchment or a lid. Freeze for at least 6 hours or overnight. To serve, leave the ice cream at room temperature for 15 minutes, then dust with the remaining ½ tbsp cocoa powder.