1. Make the crust: Put the chocolate cookie crumbs and chocolate in the bowl of a food processor fitted with the steel blade and process until the chocolate is finely grated. With the machine running, add the melted butter and vanilla, and process until evenly incorporated.

2. Transfer the mixture to a buttered 9-inch pie or tart pan and press evenly into the bottom and sides of the pan. It helps to place a piece of plastic wrap over the mixture and press on that so your hands don’t get sticky and covered with the mixture, Place in the freezer.

3. Whisk together the vanilla ice cream base and créme de menthe, and freeze in an ice cream maker, following the manufacturer’s instructions. Spread the ice cream in the piecrust, and place in the freezer until solid.

4. Thirty minutes before serving the pie, transfer to the refrigerator. Use a serrated knife dipped into hot water to slice the pie and serve. Top each serving with whipped cream, if desired.