Preheat oven to 350° F.
Sift flour, add baking powder, baking soda and salt. Sift again. Add chopped nuts. Mix well and set aside.
Melt butter. Add brown sugar and mix well. Add egg and vanilla extract. Blend well. Add flour mixture, a little at a time, mixing well. Stir in white chocolate chips. Spread in a 9-inch square pan. Bake for 20 to 25 minutes or until a wooden pick inserted in center comes out clean or with slightly fudgy-looking crumbs. Serve with ice cream and Maple Butter Sauce.
Combine syrup and butter, cook over low heat until butter is melted. Stir in brown sugar until dissolved. Add walnuts, if desired.Makes 4 Source: