Peanut Butter Fudge Brownies

adopted from the Moosewood Cookbook Fudge Brownies

butter for pan
5 oz. (5 squares) unsweetened chocolate
1/2 Lb. (2 sticks) butter, softened
1 cup peanut butter
1 3/4 cups (packed) light brown sugar (white sugar also ok)
2 tsp vanilla extract
3/4 Cup flour

1) Butter a 9x13 inch baking pan. Preheat oven to 350f
2) Melt chocolate, let cool
3) Cream butter and sugar in large bowl until light and fluffy
4) Beat in peanut butter until light and fluffy
5) Add the eggs, one at a time, beating well after each. Stir in the vanilla
6) Stir constantly while drizzling in melted chocolate.
7) Add in flour. Mix just enough to blend thoroughly
8) Spread the batter in prepared pan. Bake 20 - 25 minutes until a knife inserted into the center comes out clean. Cut into squares while still hot, then allow to cool for at least 10 minutes.