Cream butter and cream cheese; add sugar and mix until light.
Sift flour and baking powder together; stir into first mixture.
Mix well and roll into a ball.
Wrap in wax paper or foil and put in refrigerator overnight.
Roll out on floured board about 1/8 inch thick and cut into 1 1/2 inch squares.
Place on ungreased cookie sheets and sprinkle with sugar and ground cinnamon, or ground nuts and sugar, or spread with a favorite jam, or leave plain.
Bake in preheated moderate oven (375 °F.) until delicately brown.