I found this on a blog somewhere (?) and I rarely make brownies any other way these days. Yum!
Makes 12 really big brownies
Prep. Time: 15 min.
Bake Time: 30-50 min. depending on brownie box mix
1 box brownie mix (Ghirardelli!) for a 9" x 13" pan
1 c. creamy peanut butter
1/3 c. sugar
4 T. butter, melted
2 T. flour
1 t. vanilla
Preheat oven to 350. Grease a 9" x 13" pan. Prepare brownie mix according to directions on box. Prepare peanut butter swirl in mixer using the rest of the ingredients. Spread 2/3 brownie batter in pan. Drop peanut butter mixture in dollops on top. Top with remaining brownie batter. With tip of knife, cut swirls into the mixture. Bake anywhere from 30 to 50 minutes, depending on your brownie mix.