In the bowl of a mixer combine the whipping cream with the powdered sugar until stiff. (Rich Whip may be substituted for the whipping cream. Add the powdered sugar and proceed as directed.) Fold in the Creme de Menthe. Place in refrigerator for 30 minutes.

Melt the semisweet chocolate in the top of a double boiler or in the microwave. Drizzle over the whipped cream mixture and fold in (the mixture will become speckled in appearance). Pour into the prepared pie crust. Freeze at least 3 hours.