01 -
Preheat the oven to 375°F and lightly grease a deep 9-by-13-inch baking dish. In a separate pot, boil 1 pound medium shells according to the package until just tender, then drain. Reserve 1 cup cheddar and 1/2 cup mozzarella for the topping.
02 -
Cook 1 pound ground beef with the diced onion in a large skillet over medium heat, breaking up the meat. Add the minced garlic after the onion starts softening. Continue until the ground beef reaches 160°F, then carefully drain excess fat. Do not rely only on meat color.
03 -
Stir in the salt, pepper, Italian seasoning, 20 ounces undiluted condensed tomato soup, and 1/2 cup beef broth. Combine with the drained pasta, the remaining 1 cup cheddar, and remaining 1/2 cup mozzarella. Use the pasta pot for mixing if the skillet is too small.
04 -
Spread the filling in the prepared dish and top with the reserved cheeses. Cover with foil and bake about 20 minutes. Uncover and bake about 10–15 minutes more, or until the center reaches at least 165°F. Loosely cover again if the cheese browns before the middle is hot.
05 -
Let the casserole stand about 5 minutes, then scoop onto plates. Refrigerate shallow leftover portions within 2 hours, or within 1 hour if the surroundings exceed 90°F. Reheat portions to 165°F; a chilled whole casserole needs more time than the freshly assembled version.