The day before, prepare the pie crust and the apples. Boil the apple halves in syrup until tender. Cook a few at a time, and when they are done transfer carefully with a pancake turner to a flat bottomed dish. When all are cooked, pour the remaining syrup over them, cool, and put in the refrigerator.
Scald 4 1/2 cups of milk in a double boiler. Blend sugar, cornstarch, and 1/2 cup cold milk into a smooth paste. Add scalded milk gradually. Cook over hot water stirring constantly until thick. Continue cooking until no taste of cornstarch remains. Add cornstarch mixture gradually to egg yolks and return to double boiler and cook 2 to 3 minutes stirring constantly.
Remove from heat and stir in 3 tablespoons butter or margarine, 3 teaspoons vanilla, 1 cup broken nut meats, and 1 envelope unflavored gelatin softened in 1/4 cup cold water. Stir until gelatin is dissolved and cool as quickly as possible by setting pan in cold water. Stir occasionally while cooling, scraping the bottom and sides of the pan so that mixture won't congeal.
Whip heavy cream and fold into cooled pudding. Put one-half the pudding into the baked shell. Cover the pudding with the chopped dates. Spoon in the rest of the pudding over the dates. Now add the apples. Put 1/2 apple, cut side up in the center of tart. Press it down until it is even with the filling. Make a ring of apple halves around the center one. Return to refrigerator until serving time.