In a medium bowl, with a hand or stand mixer, mix together the butter, egg, and vanilla extract on medium-high speed until light and fluffy, about 2-3 minutes.
Dump the contents of the cookie in a jar into the egg & butter mixture.
Mix on medium just until the flour becomes well combined.
Cover bowl with plastic wrap and refrigerate for at least 1-2 hours.
Preheat oven to 375 degrees.
Drop large spoonfuls (about 1-2 tbsp.) of cookie dough onto a baking sheet.
Bake until lightly browned, about 10-11 minutes.
Cool cookies on the pan on a rack for 1 minute, then transfer cookies to cooling rack to cool completely.
Repeat with remaining dough.
Store cookies in a tightly covered container at room temperature for up to 3 days or store in the freezer for up to 6 months.