4 squares (4 oz.) Hershey's unsweetened baking chocolate
1 (14 oz.) can sweetened condensed milk (not evaporated milk)
2 tsp. vanilla
2 c. (1 pt.) cold whipping cream
9-inch baked pastry shell

In 2-quart glass measure or large microwave-safe bowl, place chocolate, condensed milk and vanilla. Microwave at high (100%) 2 to 4 minutes, stirring after each minute, until chocolate is melted and mixture is smooth when stirred. Cool to room temperature, about 1 1/2 hours. Beat until smooth.

In large mixer bowl, beat whipping cream until stiff; gradually fold into chocolate mixture. Pour into baked shell. Refrigerate 4 hours or until set. Refrigerate leftovers.