6. Cool cupcakes in muffin pan on wire rack until cool enough to handle, about 15 minutes. Carefully lift each cupcake from muffin pan and set on wire rack. Cool to room temperature before icing, about 30 minutes.
7. To make the Peanut Butter Frosting: Place the confectioners' sugar, peanut butter, butter, vanilla and salt in the bowl of an electric mixer fitted with a paddle attachment. Mix on medium-low speed until creamy, scraping down the bowl with a rubber spatula as you work. Add the cream and beat on high speed until the mixture is light and smooth.