Preheat the oven to 350°.
Heavily butter an 8 or 9-inch square pan. Set aside.
In a large bowl, mix all ingredients. Stir until thoroughly combined.
Press mixture into prepared pan.
Bake for 30 minutes.
Remove from oven and cool in the pan on a rack for 45 minutes.
Cut into 1 ½” squares. Dust with powdered sugar if desired.
