Cream together butter and sugar. Add egg yolk. Mix well. Combine flour and cinnamon and stir into creamed mix. Mixture will resemble coarse crumbs. Pat into greased 15x10x1 inch jelly-roll pan. Beat water and egg white until frothy. Brush over dough. Sprinkle with nuts. Bake at 350° for 20 minutes. Remove from oven and immediately cut into 3x1 inch strips.