Cream butter; add sugar, egg yolk, and flour, sifted with salt. Mix well. Spread in buttered pan, 15x10x1 inch. Brush with slightly beaten egg white. Press in almond slices. Sprinkle with cinnamon sugar. Bake in slow oven (300 F) for 50 minutes. Cut into 48 squares while hot. Cool on rack. Store in airtight container. Good keepers and shippers.