|Unsalted butter||100 Gram, softened|
|Strong black coffee||15 Milliliter (1 Spoon)|
|Cocoa powder||50 Gram|
|Plain flour||100 Gram|
|Baking powder||5 Milliliter (1 Spoon)|
Beat the butter in a mixing bowl until pale and soft.
Add 150 g/5 oz of the sugar and beat together until light and fluffy.
Beat in the egg yolk and coffee and mix well.
Sift the cocoa powder, flour, baking powder and salt together into the bowl and mix into the butter mixture until just incorporated.
Shape the dough into a roll 6 cm/2 1/2 inches in diameter.
Wrap the roll in greaseproof paper and chill for 2 hours or until firm.
Cut the dough into slices about 3 mm/ 1/8 inch thick and place on ungreased baking sheets.
Lightly sprinkle each 'wafer' with some of the remaining sugar, pressing it gently into the dough.
Bake in a preheated oven for 6-8 minutes, until the outside just darkens.
Remove to a wire tray to cool.