Fudgy espresso walnut shortbread

Preheat the oven to 180?C, gas mark 4. Lightly grease a 23cm square cake tin; line with baking parchment. Start with the shortbread. In a large bowl, beat the butter and sugar with a wooden spoon, until pale. Fold in the flour, maple syrup and a pinch of salt. Press into the tin, smooth the surface, prick with a fork and freeze for 10 minutes. Meanwhile, toast the walnuts for the topping in the oven for 8 minutes; cool and roughly chop. Bake the shortbread for 20 minutes, until golden.

For the topping, melt the butter in a pan, then simmer for 3 minutes, until the white solids turn golden and it smells toasty. Take the pan off the heat, then whisk in the remaining topping ingredients and stir in the toasted nuts. Pour onto the hot shortbread and bake for 30 minutes, until risen and set. Cool completely in the tin.

To decorate, melt the chocolate and oil in the microwave or a bowl set over a pan of simmering water. Drizzle over the bake (there will be some left over) and transfer to the fridge briefly for the chocolate to set, before cutting into squares.