Prepare brownie mix according to box instructions. Ghirardelli's mix is the very best!
Pour half batter into greased 9X9 pan.
Blend p.b., butter, vanilla, salt, and sugar until smooth.
Add cream and blend until fluffy.
Drop teaspoonfuls of peanut butter mixture into pan. Top with remaining brownie mix and twist a knife through to marble. Sprinkle with chopped peanuts.
Bake at 350 degrees for 25-30 minutes (They will be underdone!)
Allow to cool and then chill before cutting into squares.