For the truffle filling, in a saucepan, bring 2/3 cup cream to a simmer. Place the 6 ounces chocolate chips in a bowl and pour the hot cream over the chocolate. Let stand for 1 minute, then gently whisk until smooth. Spread truffle filling over the bottom of the prepared piecrust. Freeze for 20 minutes.
Meanwhile, for the whipped chocolate filling, in a double boiler or a microwave set on low power, heat the 6 ounces chocolate chips with 1/2 cup of the cream until the chocolate is just melted, stirring often. Let cool to room temperature. In a chilled bowl, beat the chocolate mixture, remainint 1 cup of cream and the vanilla until soft peaks form (tips curl). Spread the whipped chocolate mixture over the truffle filling in the crust. Refrigerate overnight.
For the topping, just before serving, beat 1 cup cream on medium speed of an electric mixer until it begins to thicken. Add confectioners' sugar and whip until stiff peaks form (tips stand straight). Spread the whipped cream over the top of the pie. Using a grater or vegetable peeler, make pieces or shavings of milk chocolate, white chocolate, and semisweet or dark chocolate. Garnish pie with chocolate pieces. Serve immediately.