- Heat oven to 300º F. Separate the egg white and yolk.
- Using an electric mixer, beat the butter, brown sugar, maple syrup, and egg yolk until smooth.
- Stir in the flour, cinnamon, and salt until combined. Spread the dough into an ungreased 15 1/2-by-10 1/2-inch jelly-roll pan or cookie sheet with sides.
- Beat the egg white in a small bowl with a fork until foamy. Spread evenly over the dough. Sprinkle on the nuts and press them gently into the dough.
- Bake 35 to 40 minutes or until the shortbread shrinks slightly from the sides of the pan. Do not overcook; you want them to be a little chewy.
- Cut diagonally into 3-by-1 1/2-inch bars.