Ingredients

• Crust:
• 3/4 cup (1 1/2 sticks) unsalted butter, at room temperature
• 1/2 cup confectioners' sugar
• 2 egg yolks
• 1/4 teaspoon salt
• 1 2/3 cups all-purpose flour
• Topping:
• 1 egg
• 2 egg whites
• 3/4 cup dark maple syrup
• 1 teaspoon maple extract, or vanilla
• 1/4 teaspoon salt
• 2 tablespoons flour
• 2 cups coarsely chopped, toasted walnuts

Instructions

1. Preheat oven to 350 degrees F.
2. To make the crust: On medium speed, cream butter with sugar until fluffy. Beat in egg yolks and salt. Stir in flour to make a stiff dough. Pat dough evenly over bottom of an ungreased 9-by-13-inch pan.
3. Bake crust in the center of the oven for 15 minutes, until set and beginning to turn golden.
4. To make the filling: Beat egg, egg whites, maple syrup, extract, and salt until smooth. Sprinkle flour over mixture and beat until dissolved. Stir in walnuts.
5. Pour the walnut mixture over the hot crust. Using potholders, pick up pan and carefully rock back and forth to distribute walnut topping evenly over crust.
6. Return to oven and bake another 20 to 25 minutes, or until topping is firm, golden, and slightly puffed. Let cool in pan, then cut lengthwise 4 times and across 10 times to make 40 skinny bars.