PREHEAT oven to 350° F.
COMBINE graham cracker crumbs, cocoa and granulated sugar in 9-inch pie plate. Stir in butter until moistened; press onto bottom and up side of pie plate.
BAKE for 8 to 10 minutes. Sprinkle 1/2 cup morsels over bottom of hot crust; let stand for 10 minutes or until all morsels are shiny. Spread chocolate over bottom and up side of crust. Cool to room temperature.
MICROWAVE 2 cups morsels and 3/4 cup cream in large, uncovered, microwave-safe bowl on HIGH (100%) power for 1 minute; STIR. The morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until morsels are melted. Cool to room temperature.
BEAT remaining cream, powdered sugar and vanilla extract in chilled small mixer bowl until soft peaks form. Fold 2 cups whipped cream into chocolate mixture. Spoon into crust; swirl top. Garnish with remaining whipped cream. Refrigerate until firm.
MICROWAVE remaining 1/4 cup morsels in heavy-duty plastic bag on HIGH (100%) power for about 30 seconds; knead until smooth. Cut tiny corner from bag; squeeze to drizzle chocolate over pie. Llet stand a few minutes before serving.