In a mixing bowl, stir together the Oreo cookie crumbs, granulated sugar, and melted salted butter. Portion the crumbs into the mini cheesecake pan using a small cookie scoop (about 1 tablespoon). Firmly press the crumbs into the bottom of the pan to form the crust. Set aside.
In a large bowl, use an electric hand mixer to cream the cream cheese, powdered sugar, peanut butter and vanilla extract until smooth. Pour in the heavy cream and whip the cheesecake mixture on medium-high speed until the mixture thickens and becomes light and fluffy.
Fill a piping bag with the peanut butter cheesecake mixture and pipe it onto the chocolate cookie crusts, slightly above the top of the pan. Chill the cheesecakes in the refrigerator for 12 hours or overnight. After chilling, remove the cheesecakes from the pan.
To make the chocolate ganache, combine the semisweet chocolate chips and heavy cream in a microwave-safe bowl. Heat the chocolate and cream in the microwave in 15 second intervals, stirring in between each interval, until the chocolate is melted and the ganache is smooth. Set aside to cool slightly.
To make the whipped cream, in a bowl with an electric mixer, whip the heavy cream, powdered sugar and vanilla extract until medium-stiff peaks form. Fill a piping bag fitted with a Wilton 1M piping tip with the whipped cream.
To assemble the cheesecakes, pipe or spoon the slightly cooled chocolate ganache on the top of the cheesecakes. Pipe a small swirl of whipped cream on top of the ganache. Sprinkle the cheesecakes with Oreo cookie crumbs and top each cheesecake with a mini peanut butter cup.