1. In a bowl cream butter until light and fluffy.
Gradually stir in peanut butter, then gradually beat in confectioners' sugar until mixture is soft and fluffy.
2. Dip biscuits quickly, one by one, into cold coffee and place 16 of them, touching, on a foil-lined cookie sheet (4 biscuits lengthwise and 4 biscuits across). Spread biscuits with quarter of the peanut butter mixture, spreading mixture carefully into an even layer. Sift over quarter of the cocoa. Repeat until you have 4 layers of biscuits. Spread remaining peanut butter mixture over the top and sides of the cake; dust with remaining cocoa; sprinkle top and sides with chopped peanuts.
3. Refrigerate for dozen hours. Slice thinly and serve while still cold.