In a large bowl, cream together the peanut butter and powdered sugar until you have a smooth mixture.

In a separate bowl, whip the heavy cream and vanilla extract until stiff peaks form. Be careful not to overwhip!

Gently fold the whipped cream into the peanut butter mixture until just combined. You want to maintain some air from the whipped cream for a lighter filling.

Spoon the filling evenly into the mini graham cracker crusts. Use a spatula to smooth out the tops.

Refrigerate the pies for at least 2 hours, or until the filling is set.

When ready to serve, garnish with chocolate shavings or mini peanut butter cups, if desired.