To Make Crust: In a medium mixing bowl combine graham cracker crumbs, sugar, and melted butter. Mix all together and press mixture firmly into a 9 inch pie pan.
To Make Fudge Layer: In a medium mixing bowl combine flour, baking powder, and salt. Mix well. In a double boiler melt semisweet chocolate and unsweetened chocolate together with 1/2 cup butter or margarine, stirring until smooth. Cool slightly.
Meanwhile beat sugar, whole egg, and egg white in a medium bowl until slightly thickened. To this mixture add vanilla and cooled chocolate. Mix until well blended. Stir in dry ingredient mixture and mix until just combined. Pour mixture into crust and bake in preheated oven for about 17 minutes, or until just set. Cool on a rack for 10 minutes. Place candy bar slices on this layer.
To Make Cream Cheese Layer: In a medium mixing bowl beat cream cheese and sugar until blended. Add egg and vanilla extract and beat until smooth. Spread mixture over candy bars and bake for 15 minutes, or until set. Cool on rack.
To Make Garnish: In a small saucepan stir milk chocolate and whipping cream over low heat until smooth. Drizzle over pie. Refrigerate and serve chilled.