In a bowl, beat eggs and 1/2 cup sugar until thickened. Combine baking powder and remaining sugar; beat into egg mixture. Add crumbs, dates, nuts, orange zest and vanilla; stir well. Pour into a well-greased 10-in. pie plate or 11x7-in. baking pan. Bake at 350° for 30-40 minutes or until a toothpick comes out clean. Combine topping ingredients; let stand at room temperature until pie has cooled for 30 minutes (topping will thicken). Spread over pie. Cool completely. Store in the refrigerator.