Preparation - Mix the first four ingredients together in a saucepan. Cook, stirring constantly just until boiling. Lower the heat and simmer gently for 2 to 3 minutes. Remove from heat and set aside. In a mixing bowl, mix the eggs, sugar and butter together. Beat for 2 to 3 minutes. Mix the flour and baking powder together in a bowl. Alternately add the flour/baking powder mixture and the milk to the egg mixture and beat well. Add the vanilla and mix well. Divide the batter in three, pouring it into the 3 unbaked pie shells. Pour the chocolate mixture over the batter in each of the pie shells. The chocolate mixture will be very runny but it will thicken and "sink" below the batter as it bakes. Bake in a preheated oven at 350º for 35 to 40 minutes or until the cake springs back when pressed gently in the center.