Prepare Shortbread recipe through step 1. Press dough evenly into the bottom of a greased 9- by 9-in. baking pan. Bake 10 minutes.
Meanwhile, in a small saucepan, bring 3 tbsp. butter, 1/3 cup honey, and 1/3 cup sugar to a boil. Remove from heat.
Stir in 3/4 cup each toasted whole almonds, pecan halves, salted cashews, and salted pistachios.
Carefully spoon mixture over shortbread and continue to bake until nuts are toasted and liquid is bubbling, about 30 minutes. Let cool.
Use a serrated knife to cut into 16 squares; cut each square diagonally to make 32 triangles.