Butter a 20cm square cake tin and line with baking parchment. For the streusel, mix the flour, espresso, sugar and cardamom in a bowl. Rub in the butter until the mixture resembles coarse breadcrumbs, then press bits together – you want a mixture of large and small crumbs. Chill until needed. Combine the filling ingredients and set aside.

Heat the oven to 180C/160C fan/gas 4. For the cake, mix the flour, baking powder, espresso and cardamom together in a bowl and set aside. Beat the butter and both sugars together in a separate bowl using an electric whisk until creamy, about 4-5 mins. Add the eggs one at a time, beating well after each addition, then beat in the soured cream and vanilla until smooth. Fold in the flour mixture. Spoon half the batter into the tin, then sprinkle over the filling. Dollop over spoonfuls of the cake batter and smooth out. Sprinkle over the streusel and bake for 35-40 mins until a skewer inserted into the centre comes out clean. Cool in the tin for 20 mins, then remove to a wire rack to cool completely. Cut into squares. Will keep in an airtight container for up to five days.