In a medium bowl, combine graham cracker crumbs and melted butter. Press mixture into the bottoms and sides of a muffin tin lined with cupcake liners. Refrigerate for 30 minutes.

In a large mixing bowl, beat the cream cheese and peanut butter until smooth. Add powdered sugar and vanilla extract, and mix until well combined.

In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the peanut butter mixture.

Spoon the peanut butter filling into the chilled crusts, smoothing the tops with a spatula.

In a small saucepan, heat the 1/2 cup heavy cream until just simmering. Remove from heat and add the chocolate chips, stirring until melted and smooth.

Pour the chocolate ganache over the peanut butter filling, spreading evenly.

Refrigerate the pies for at least 2 hours, or until set. Garnish with additional chocolate chips before serving.