Preheat oven to 325°. In a food processor, grind cookies into fine crumbs. Drizzle in melted butter and whirl until crumbs start to come together.
Press crumb mixture firmly over bottom (not sides) of pan called for by recipe.
Bake until crust is set, about 10 minutes. Let cool completely.
*If cookies are really buttery, start with 2 tbsp. butter and add only enough extra butter to make crumbs cling together.
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