Rhubarb Custard Pie
["1 egg, slightly beaten", "1 c. sugar", "3 Tbsp. flour", "1/2 c. water", "1 Tbsp. butter or margarine", "3 c. rhubarb, cut in 1/2-inch pieces", "1 unbaked pie shell"]
["Mix all ingredients, except rhubarb, and let stand while preparing the crust. Pour mixture over rhubarb in shell.", "Bake 45 minutes at 375\u00b0 or until done."]
["egg", "sugar", "flour", "water", "butter", "rhubarb", "shell"]