Melt the butter in a pan. Pour into a mixing bowl. Stir in the sugar. Allow to cool.
Mix together the flour, baking powder and salt.
Add the eggs to the butter-sugar mixture and mix until well incorporated. Add the flour mixture and mix well. Add the vanilla extract, chopped pili nuts and chocolate morsels. Stir until well blended. The batter will be moderately heavy.
Transfer to a greased 8" x 8" baking pan. Spread evenly, using a spatula. Bake in a 180C oven for 25 minutes.
Remove the baking pan from the oven, transfer to a wire rack and cool before cutting the butterscotch brownies into two-inch squares.