Shortbread
1/2 cup unsalted butter
1/4 cup granulated sugar
1 cup all-purpose flour

Preheat oven to 350 degrees F. Butter a 9-inch square pan.

Cream butter and sugar until light and fluffy. Add flour and mix until just blended. Pat into bottom of prepared dish. Bake until shortbread is light brown, about 25 minutes.

Maple Topping
3/4 cup firmly packed brown sugar
1/3 cup maple syrup
1 tablespoon unsalted butter (at room temperature)
1 egg (at room temperature)
1 teaspoon vanilla extract
1/2 cup chopped toasted walnuts

Beat sugar, maple syrup and butter to blend. Beat in egg and vanilla extract. Pour over shortbread. Sprinkle with walnuts. Bake until topping is set, about 25 minutes. Cool on rack.

Cut into 1 1/2 inch squares. Store in airtight container.