Place the peanut butter cookies in a food processor and pulse until finely ground. Alternatively, place them in a sealed bag and crush with a rolling pin.
In a medium bowl, combine the crushed cookies and sugar. Pour the melted butter over the mixture and stir with a fork until all crumbs are moistened.
Transfer the mixture to a 9-inch pie plate or springform pan. Press firmly and evenly into the bottom and up the sides using the bottom of a measuring cup or your fingers.
Refrigerate for at least 30 minutes before filling, or freeze for 15 minutes for a firmer crust.
Tips
For a gluten-free crust, use gluten-free peanut butter cookies.
If the crust is too crumbly, add an extra tablespoon of melted butter.
Store leftover crust (unfilled) in the refrigerator for up to 5 days, or freeze for up to 3 months.