Beat eggs and 1/2 cup sugar until thick, about 5 minutes. Combine baking powder with the remaining sugar, beat into the egg mixture. Add the crumbs, dates, nuts, zest and vanilla. Stir well. Pour into a well greased 10" pie pan or a 11x7x2 baking dish. Bake 350º for 30-40 minutes or until a toothpick comes out clean.
Combine the topping ingredients; let stand at room temp until the pie has cooled for 30 minutes (Topping will thicken). Spread over the pie. Cool completely. Store in the refrigerator.