1.Heat the oven to 400°F. Beat the egg and water in a small bowl with a fork. 2.Stir the Muenster cheese, Parmesan cheese, onion and garlic powder in a medium bowl. 3.Sprinkle the flour on the work surface. Unfold the pastry sheet on the work surface. Brush the pastry sheet with the egg mixture. Top with the cheese mixture and spinach. Starting at a short side, roll up like a jelly roll. Cut into about 20 (1/2-inch) slices. Place the slices, cut-side down, onto 2 baking sheets. Brush the slices with the egg mixture. 4.Bake for 15 minutes or until the pastries are golden brown. Remove the pastries from the baking sheets and let cool on wire racks for 10 minutes. 5.For best results, make sure to remove as much liquid as you can from the spinach before adding it to the pastry. If it's too wet, it may make the pastry soggy. 6.For Pesto Swirls, omit all ingredients but the flour and the puff pastry. Unfold the pastry sheet as directed above. Spread 1/2 of an 8-ounce package cream cheese, softened, on the pastry sheet to within 1/2 inch of the edge. Top with 3 tablespoons pesto sauce and sprinkle with1/4 cup finely chopped walnuts. Brush the edge of the pastry sheet with water. Roll up the pastry and proceed as directed above. 7.For Ham & Broccoli Swirls, omit the spinach, cheeses, onion and garlic powder. Unfold the pastry sheet and brush with the egg mixture as directed above. Spread 1/2 of an 8-ounce container whipped cream cheese with chives on the pastry sheet. Top with 1 cup frozen chopped broccoli, thawed and well drained and 1 cup finely chopped cooked ham. Proceed as directed above. 8.For a flavor twist, try a different cheese. Any shredded cheese will work in this recipe.