Cream together softened butter and brown sugar. Add eggs and vanilla. Seperate bowl combine flour, baking powder, and salt. Slowly add to wet mixture. Fold in walnuts and buttescotch chips. Spread in a 9x13 greased pan, and Bake at 350 for approx 25 min.
For the Maple Butter Sauce combine Maple syrup and butter and cook on low till butter is melted. Stir in brown sugar until dissolved. Add walnuts.