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Preheat oven to 300°F. Beat butter and granulated sugar in large bowl with electric mixer on high speed until light and fluffy. Add egg yolk; beat well. Add flour and cinnamon; beat on low speed until well blended.
Press dough evenly into a 1/4-inch thick rectangle on large (at least 15x12-inch) ungreased baking sheet. Beat egg white until foamy. Brush on dough. Sprinkle evenly with nuts; lightly press into dough.
Bake 35 to 40 minutes or until lightly browned. While still hot, cut into 2 1/2 x 1 1/2-inch bars. Remove from baking sheet. Cool completely on wire rack.
Mix confectioners' sugar and water in small bowl until smooth. Drizzle over cooled bars. Let stand until glaze is set.