Method

​1 Preheat the oven to 170°C/fan 150°C/gas mark 3 and line two baking trays with baking parchment paper.

2 To make the dough, combine the gluten-free 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. Dissolve the coffee in 1 teaspoon of boiling water. Beat the egg with a fork and mix in the coffee. Add to the bowl and stir into the mixture with a wooden spoon to make a firm dough.

3 Tip the dough on to a work surface and divide into 16 pieces. Flour your hands well, then shape each piece into a neat ball. Arrange them with sufficent space on the prepared baking trays to allow for spreading. Bake in the pre-heated oven for 12-15 mins, until light-golden and firm to the touch.

4 Leave to cool for a couple of minutes, then transfer to a wire rack and leave to cool completely.

5 For the icing: beat the butter and icing sugar together in a small bowl until pale and light. Add the coffee and mix well. Use the buttercream to sandwich the biscuits together in pairs.