1Cream the butter and sugar. Add the egg yolk and beat thoroughly. (This should be very creamy.) Add the flour and cinnamon and mix well.
2Spread thinly on 1 1/2 cookie sheets. Press down mixture with fingers, then score with a fork. Brush on a film of egg white mixed with a little water. Sprinkle the nuts over the top.
3Bake 1/2 hour at 300 degrees F (150 degrees C). Remove from oven and cut into squares or oblongs. When cold, remove from cookie sheet.