Directions

Preheat oven to 350°F and butter an 8 by 8-inch baking pan. Sift together all purpose and whole wheat flours, baking powder and salt.  Set aside. Melt butter and add to brown sugar, whisking until smooth.  Add vanilla and eggs, one at a time.  When mixture is uniform and ingredients well combined, fold in dry ingredients using a spatula.  Add optional nut butter and nuts, if using. Bake in center of oven for 30 to 40 minutes rotating pan halfway through baking time.  The bars are ready when the edges pull away slightly from the sides of the pan and the top is golden brown.  Cool on a rack before cutting.