2In a large bowl, mix together the uncooked ground beef, onion, dry pasta, diced tomatoes with their juice, bone broth, tomato paste, mustard, 1 cup of the shredded cheese, salt, and pepper.
3Divide the mixture evenly among four oven-safe 600 ml glass bowls.
4Cover each bowl tightly with aluminum foil.
5Place the bowls on a baking sheet and bake for 20 minutes.
6Remove from oven, carefully uncover, and stir each portion.
7Top each bowl with the remaining cheese.
8Return to oven, uncovered, and bake for an additional 5-7 minutes, or until cheese is melted and bubbly.