Guests will be sure to save room for these delicious cookie bars, which also make great homemade gifts.
Preheat oven to 300°F. Beat butter and 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 with nuts, pressing nuts lightly into dough.
Bake 45 minutes or until lightly browned. While still hot, cut into 36 bars, 2 1/2x1 1/2-inch each. Remove from baking sheet. Cool completely on wire rack.
Melt chocolate chips in separate bowls as directed on package. Spoon each melted chocolate into a small resealable plastic bag. Cut a small piece from one of the bottom corners of each bag. Close bags tightly, then drizzle the chocolates in a decorative pattern over the bars. Let stand until chocolate is set. Store in an airtight container.