Put the cookies in a food processor and pulse until finely ground; transfer to a bowl. Add the brown sugar and cinnamon and mix to combine. Pour in the melted butter and stir until the cookies are evenly coated with the butter.
Press the mixture into a 9-inch pie plate to form a pie crust, making sure that all surfaces are even. If you're making a no-bake pie, bake the crust before adding the filling: Bake at 375 degrees F until the crust is dry, about 10 minutes; the time will vary depending on how crispy the cookies are. If the pie you are preparing is baked, do not pre-cook the crust. Add the filling and cook the pie according to the recipe instructions.
This is a great opportunity to make use of overbaked, not-so-perfect cookies.