Crust: Position rack in center of oven and preheat to 350 degrees F. Grease a 9" diameter deep-dish glass pie plate. Combine graham cracker crumbs and sugar in a medium bowl. Add melted margarine and stir until well incorporated. Press graham mixture evenly into bottom and up sides of prepared dish. Bake until crust is set, about 5 minutes. Cool on rack. Maintain oven temperature. Fudge Layer: Sift flour, baking owder, and salt into medium bowl. Combine margarine, semisweet and unsweetened chocolate in top of double boiler set over simmering water. Stir until melted and smooth. Remove and cool slightly. Using electric mixture, beat sugar, egg, and egg yolk in medium bowl until slightly thickened, about 1 minute. Add vanilla and cooled chooclate mixture and mix until well blended. Add dry ingredients and mix just until combined. Pour fudge mixture into crust. Bake until almost set and tester inserted into center comes out with moist batter still attached, covering crust if browning too quickly, about 17 minutes. Cool on rack for 10 minutes. Arrange Snickers pieces over fudge layer. Cream Cheese Layer: Using electric mixer, beat cream cheese and sugar in medium bowl until smooth. Add egg and vanilla; beat just until smooth. Carefully spread mixture in pie. Bake until cream cheese layer is set, about 15 minutes. Cool on rack.