Step 1

In a large skillet, cook beef and onion over medium heat until the meat is no longer pink, breaking meat into crumbles; drain. Stir in the water, tomato paste, bouillon and oregano. Cover and simmer for 30 minutes.

Step 2

Meanwhile, in a large bowl, combine the ricotta cheese, 1 cup mozzarella, Parmesan cheese and egg. Stuff shells with the cheese mixture.

Step 3

Arrange shells in a greased shallow 3-qt. or 13x9-in. baking dish. Spoon meat sauce over shells. Cover and bake at 350° for 30 minutes. Uncover; sprinkle with remaining mozzarella cheese. Bake until cheese is melted, 3-5 minutes longer.