Preheat the oven to 180°C/gas mark 4.
Grease and line 2 x 8 in (20cm) sandwich tins with baking parchment.
Cream together the butter and sugar until pale, light and fluffy.
Add the lightly beaten eggs, a little at a time. Sieve in a tablespoon of flour along with each addition of the eggs to prevent the mixture from curdling.
Once all the egg mixture has been incorporated, sieve and fold in the remaining flour.
Stir through the cooled espresso until evenly distributed.
Divide the cake mixture between the two lined tins. Bake for 20–25 minutes, until well risen and golden brown.
Remove from the oven and allow to cool for 2 minutes before turning the cakes out onto a wire rack to cool completely.