In a mixing bowl, cream butter and sugar. Beat in egg yolks and extract. Combine flour, salt and baking powder; gradually add to creamed mixture. Stir in almonds. Cover and chill at least 2 hours. Roll out on a lightly floured surface to 3/8-inch thickness. Cut with cookiecutters; place on ungreased baking sheets. Sprinkle with sugar if desired. Bake at 375° for 10-13 minutes or until the edges begin to brown. Cool on wire racks. Frost if desired.