Preheat oven to 325°. Put flour, butter, granulated sugar, and salt in the bowl of a stand mixer. Mix on low speed until blended, then increase to medium and mix until dough is no longer crumbly and just comes together.
Press dough evenly into the bottom of a greased 9- by 9-in. baking pan. Bake 10 minutes.
Meanwhile, make topping: In a small saucepan, bring butter, honey, and sugar to a boil. Remove from heat. Stir in nuts. Carefully spoon mixture over shortbread and continue to bake until nuts are toasted and liquid is bubbling, about 30 minutes. Let cool completely. Use a serrated knife to cut into 16 squares, then cut each square diagonally to make 32 triangles.
Note: Nutritional analysis is per cookie.