For crust, combine crushed wafers and melted margarine; press onto bottom of 8x8x2-inch dish. Dissolve coffee crystals in 1 tablespoon hot water. Beat together 1/2 cup sugar and 1/2 cup margarine until fluffy. Add egg yolks, one at a time, beating well after each. Add coffee, chocolate and vanilla; beat until combined. Beat egg whites to soft peaks; gradually add remaining sugar, beating to stiff peaks. Fold chocolate mixture into egg whites. Spread over crust. Sprinkle toffee atop. Cover; freeze 6 hours or until firm. Let stand 5 minutes before serving.