Process first 3 ingredients and 1/3 cup brown sugar in a food processor until crumbly. Press mixture into bottom and up sides of a 10-inch deep-dish pieplate.
Bake at 350° for 5 minutes. Set piecrust aside.
Beat remaining 1 cup brown sugar, cream cheese, peanut butter, and 1 tablespoon whipping cream at medium speed with an electric mixer until mixture is light and fluffy.
Beat remaining whipping cream and vanilla until stiff peaks form. Fold one-third whipped cream into peanut butter mixture; fold peanut butter mixture into remaining whipped cream.
Slice bananas, and place on crust. Spread peanut butter mixture evenly over bananas. Sprinkle with chopped peanuts, if desired. Chill 2 hours.
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