Preheat oven to 425°F (220°C).
In a large bowl, mix together the uncooked ground beef, onion, pasta, diced tomatoes with their juice, bone broth, tomato paste, mustard, 1 cup of the shredded cheese, salt, and pepper.
Divide the mixture evenly among four oven-safe 600 ml glass bowls.
Cover each bowl tightly with aluminum foil.
Place the bowls on a baking sheet and bake for 20 minutes.
Remove from oven, carefully uncover (watch for steam), and stir each portion.
Top each bowl with the remaining cheese.
Return to oven, uncovered, and bake for an additional 5-7 minutes, or until cheese is melted and bubbly.
Let cool for 3-5 minutes before serving.