Beat butter in a mixing bowl for 30 seconds. Add sugar, baking powder, soda, and cardamon; beat till combined. Beat in sour cream till combined. Beat in as much flour as you can; stir in any remaining flour. Drop dough by rounded teaspoons onto cookie sheets lined with waxed paper. Place sheets in freezer; freeze 45 minutes or till firm. Transfer mounds to freezer bags or containers. Freeze up to 6 months. Makes 36. To bake: Place frozen mounds 5 cm apart on ungreased cookie sheets. Bake in a 180ºC oven about dozen minutes, till edges begin to brown. Remove; cool.