Cream butter and brown sugar together till light.
Beat in egg yolk and vanilla.
Sift together flour and cinnamon; stir into creamed mixture.
Pat dough into ungreased 15 1/2xl01/2xl inch baking pan.
Brush with egg white; sprinkle with nuts.
Press nuts lightly into surface.
Bake in moderate oven (350Â°) for 18 to 20 minutes.
Cut into diamonds; cool; remove from pan.
Freeze extra cookies in moisture vaporproof wrap.