In a medium size bowl combine chicken, Ricotta and Jack cheeses, chiles, egg and onion. Wrap tortillas in a paper towel. Microwave at high (100%) until pliable, 45 seconds to 1 minute. Place filling in tortillas and roll, jelly roll fashion. Pour half the enchilada sauce in the bottom of a 2 quart oblong baking dish. Place enchiladas in dish and pour remaining sauce over top. Cover with wax paper. Microwave at high (100%) until heated through, 8 to 10 minutes. Sprinkle with Cheddar cheese. Microwave at high (100%) until cheese is melted, 1 to 2 minutes. Makes 6 servings.