In a large bowl, combine 3/4 cup softened butter, peanut butter, and vanilla. Beat with an electric mixer on medium speed for 30 seconds. Add icing sugar and beat until combined, scraping bowl occasionally. Beat in the 2 tablespoons whipping cream. Stir in the chopped peanuts. Spread mixture evenly over the cooled crust. Place bars in the refrigerator while preparing the ganache.