Preheat the oven to 350 degrees F.

Place 1/2 pound of the butter and the brown sugar in the bowl of an electric mixer fitted with the paddle attachment. Cream the butter and sugar on medium speed until a smooth batter is formed. While the machine is running, add the eggs and vanilla extract, until incorporated into the batter.

Sift together 3 cups flour and baking powder. Slowly add the flour mixture to the batter and mix on low speed until a dough is formed. Very gently, by turning the mixer on and then off, fold the chips and nuts into the dough.

Once the dough is all blended, grease a 9 by 9-inch baking pan with the remaining butter and dust with the 1 tablespoon of flour. Pour the batter into the pan and place in the preheated oven. Bake for 25 to 30 minutes, or until set yet still moist.