In a medium saucepan, bring the cream, milk, and mint to a gentle boil. Remove from the heat.
In a bowl, whisk together the egg yolks and sugar until thick. Whisk 1 cup of the hot cream into the egg mixture. In a slow, steady stream, gradually add the egg mixture to the pan of hot cream. Cook over moderately low heat, stirring occasionally, until the mixture thickens enough to coat the back of a spoon and reaches 170 degrees F on an instant-read thermometer, 3 to 5 minutes.
Remove the pan from the heat and strain the mixture into a clean bowl through a fine mesh strainer. Pour into a container and cover with waxed paper or plastic wrap, pressing down against the surface to keep a skin from forming. Chill in the refrigerator for at least 2 hours.
When cold, stir in the mint liqueur and chocolate chips. Pour into the bowl of an ice cream machine, and churn and freeze according to manufacturer’s instructions. When the ice cream has come together, transfer to the chocolate cookie crust and finish the ice cream pie, or transfer to an airtight container and place in the freezer until ready to use.
To Assemble Ice Cream Pie:
Place the piecrust in the freezer for at least 1 hour. Remove the ice cream from the freezer and let sit at room temperature until soft enough to spread, 5 to 10 minutes.
Remove the crust from the freezer and unwrap. Transfer the ice cream to the piecrust, filling to the top, and smooth with a spatula or the back of a spoon. Place in the freezer until firm, and serve.
Yield: Makes 1 ice cream pie, about 8 servings