- STEP 1
Preheat the oven to 170°C/325°F/gas 3.
- STEP 2
To make the dough, combine the flour and sugar in a mixing bowl. Add the butter and rub into the flour mixture using the tips of your fingers, until the mixture looks like fine crumbs.
- STEP 3
Dissolve the coffee in 1 teaspoon of boiling water. Beat the egg until frothy and mix in the coffee. Add to the bowl and stir into the mixture with a wooden spoon.
- STEP 4
Tip the dough onto a well floured work surface and divide into 16 pieces. Flour your hands well then shape each piece into a neat ball. Arrange them well apart on the prepared baking trays (to allow for spreading) and bake in the heated oven for 12 to 15 minutes, until light golden and firm to the touch.
- STEP 5
Leave to cool for a couple of minutes, then transfer to a wire rack and leave to cool completely.
- STEP 6
Make a simple buttercream by beating the butter with the icing sugar and cocoa powder, if using. When very light and smooth, use to sandwich the biscuits in pairs.