Preheat oven to 400 degrees F. In a small bowl, combine egg and the water; set aside. Line a large baking sheet with parchment paper; set aside. Unfold pastry onto a lightly floured surface. Roll pastry into a 12-inch square. Using a pizza cutter, cut a 1/2-inch strip from each of the four sides of the square. Brush edges of pastry square with egg wash. Transfer pastry to prepared baking sheet. Attach a pastry strip to each side of the square to form an edge; brush again with egg mixture. Prick pastry with a fork.
In a small bowl, stir together sugar and ginger. Arrange apple slices over pastry, overlapping as necessary. Sprinkle with sugar mixture.
Bake for 20 to 25 minutes or until pastry is deep golden brown and crisp. Cool on baking sheet on a wire rack. Transfer to a cutting board or platter.
Nutrition Information for Ginger-Apple Tart Servings Per Recipe: 12 PER SERVING: 120 cal., 7 g total fat 18 mg chol., 83 mg sodium, 14 g carb. (1 g fiber, 6 g sugars), 1 g pro.