Beat butter and peanut butter at medium speed with an electric mixer until blended. Add powdered sugar and vanilla wafer crumbs; beat until blended. Press mixture evenly into a lightly greased 13- x 9-inch baking pan lined with wax paper.
Stir together chocolate morsels and whipping cream in a medium saucepan over low heat until melted and smooth. Spread evenly on top of peanut butter mixture. Chill 1 hour or until firm.
Remove from refrigerator, and let stand at room temperature 10 minutes or until slightly softened. Cut into 48 bars.