Jane's Blonde Brownies

This is Jane Dunlap's recipe for Blondies. She always makes them and they are so good and every time I made them they were crap. It was very frustrating, then I figured out why. She always doubles the original recipe she gave me and bakes it in an 8x8 pan for less time than she told me. So I was essentially using a halved recipe as the whole and baking it in a bigger pan for a longer amount of time - this = not good blondies. Here's the goods:

1/2 cup butter
1 1/2 cup flour
2 cup brown sugar
2 eggs
1 1/2 tsp baking powder
1 tsp salt
1 tsp vanilla
1 cup chopped nuts (optional)

Melt butter over low heat. Remove from heat and add brown sugar, stir until well blended. Cool. Add eggs and mix well. Stir in dry ingredients. Add vanilla and nuts. Bake at 350* for 18-20 minutes.