Line a baking sheet with baking paper. Put the almonds, sugar and baking powder in a bowl and stir through the beaten egg white to make a soft paste. Knead briefly, then roll into a long cylinder. Slice off 1 cm (1/2 inch) pieces and lightly pinch each end to make oval shapes. Place on the baking sheet and bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 10 minutes or until pale golden. Leave to cool and dust with plenty of icing sugar.
Meanwhile, make the cocktail. Mix together the coffee and coffee liqueur and pour into 4 martini glasses. Slowly pour in the cream over the back of a teaspoon so it settles on the top. Serve with the biscuits.