1Cream 1 cup butter or margarine. Gradually add brown sugar, creaming well. Add egg yolk and blend. Add flour, stirring until the mixture forms a dough. Chill slightly for easier handling.
2Roll dough into small balls, about the size of a marble. Place on an ungreased baking sheet and flatten to 1/8 inch thickness with the palm of the hand. Press with fork in one direction to make a design.
3Bake at 325 degrees F (165 degrees C) for 9 to 12 minutes until cookies just begin to brown very lightly. Remove from sheet while warm. Place flat sides of two cookies together with frosting, sandwich-style.
4To Make Browned Butter Frosting: Brown 2 tablespoons butter slightly in saucepan. Remove from heat and blend in 1 1/4 cups sifted confectioners' sugar. Gradually add 1/2 teaspoon vanilla and 4 to 5 teaspoons cream until it becomes a spreading consistency.