Preheat the oven to 350 degrees F.
Combine 1/2 cup of margarine and 1 cup of flour in a medium mixing bowl and mix with your hands until completely blended. Sprinkle 2 tbs. of water over the dough and stir with a spoon.
Gather the pastry dough into a ball and divide into halves. Pat each half into a rectangle about 12 inches by 3 inches. Place the rectangles onto an ungreased cookie sheet spaced about 3 inches apart.
Heat 1/2 cup of margarine and 1 cup of water into a rolling boil in a medium pot. Remove from the heat and quickly stir in the apple juice concentrate and 1 cup of flour. Stir vigorously until the mixture forms a ball. Remove the pot from the stove.
Beat in the eggs until the mixture is smooth and glossy. Spread half of the topping onto each of the pastry rectangles.
Bake for 1 hour, or until the top of the pastry is crisp and brown.
Combine the powdered sugar, margarine and vanilla in a mixing bowl and spread on top of the cooled pastries.