Preheat your oven to 350°F (175°C) and prepare your baking dish.

In a large skillet, cook the ground beef over medium heat until browned, about 6–8 minutes.

Melt butter in the skillet and sauté onion and bell pepper for about 4 minutes until softened.

Combine the beef with the sautéed vegetables and mix in ketchup, Worcestershire sauce, salt, and pepper, cooking for about 2 minutes.

Remove from heat and fold in half of the cheddar cheese until melted.

Cook the pasta shells according to package instructions until al dente, then stuff with the beef and cheese mixture.

In the skillet, combine beef broth, milk, and cornstarch over medium heat, whisking until thickened, then stir in remaining cheddar.

Pour half of the cheese sauce around the stuffed shells in the baking dish.

Bake for about 10 minutes until cheese is bubbly and melted.

Drizzle remaining cheese sauce on top before serving.