Line an 8×8 inch pan with parchment paper. In a large bowl, cut butter into a few chunks. Measure and mix dry ingredients and then dust over butter. Using fingers, crumble butter and dry ingredients until well combined and crumbly. Press mixture into lined baking pan and press firmly. Refrigerate for 10 to 20 minutes.

Preheat oven to 300º F. Bake prepared dough for 25 to 30 minutes. Remove from oven and using a straight metal spatula, cut straight up and down, not slicing or mixture will crumble apart. Cut in this manner to make 16 squares. Let cool. Remove from pan by lifting out with the parchment paper lining. Gently pull apart pieces and move to a serving plate. Dust with powdered sugar. Serves 16.