Heat oven to 400 degrees. Coat a 2-½- to 3-quart shallow glass baking dish with vegetable or olive-oil spray. In a large bowl, whisk together 1 cup of the mozzarella with cottage cheese or ricotta, egg, and oregano. Make a thin, even layer of one-third of the potatoes in the bottom of the prepared dish. Next make a layer of one-third of the cheese mixture, spreading it evenly over the potatoes. Add one-third of the tomato sauce. Continue layering, finishing with a layer of sauce. Sprinkle the top of the casserole with the remaining ½ cup of mozzarella and the Parmesan cheese. Cover the baking dish tightly with foil. Bake 40 minutes. Remove foil, return to oven, and continue baking 15 to 25 minutes, until potatoes are tender when pierced. Let the lasagna stand about 10 minutes before serving.