01 -
Set oven to 175°C (350°F) to preheat.
02 -
In a large skillet over medium-high heat, cook ground beef and chopped onion, breaking meat into small pieces until beef is browned. Drain excess fat.
03 -
Season the beef mixture with salt, black pepper, and onion powder. Add Worcestershire sauce and cook for 1 minute. Stir in tomato soup and water, reduce heat to low, and let simmer for 5 minutes.
04 -
Incorporate half of the shredded cheddar and reserved pasta water into the meat sauce. Stir in cooked pasta shells and combine thoroughly.
05 -
Transfer mixture to a greased 33 x 23 cm (9 x 13 in) baking dish. Evenly sprinkle remaining cheddar cheese over the top.
06 -
Place baking dish on center oven rack and bake for 30 minutes until cheese is melted and casserole is bubbling.
07 -
Allow casserole to rest for 5–10 minutes. Garnish with chopped parsley if desired. Serve warm.