Preheat oven to 350. Spray 8-inch square pan with cooking spray.
Melt butter over low heat in small saucepan. Once melted, remove from heat. Add brown sugar and stir until smooth. Add beaten egg and incorporate well. Sift the flour and baking powder together and stir into the brown sugar mixture. Add the vanilla, walnuts and ginger and mix well.
Pour batter into pan and bake for 20-22 minutes (do not overbake! The bars should yield to a light touch).