Start by bringing a large pot of salted water to a boil. Add the pasta shells and cook until al dente, about 7-10 minutes. Drain and set aside.

In a skillet over medium heat, add olive oil. Sauté chopped onion for 3-4 minutes until translucent. Stir in minced garlic and cook for an additional 30 seconds.

Increase heat and add ground beef, breaking it up as it cooks until browned, about 6-8 minutes. Drain excess fat.

Reduce heat to medium-low, stir in tomato paste and cook for 1-2 minutes. Add diced tomatoes, beef broth, and Italian seasoning, simmer for 5 minutes.

Lower heat and mix in heavy cream until warm, then gently incorporate cooked pasta shells.

Sprinkle in half of the mozzarella and Parmesan cheese, stir until melted. Top with remaining cheese and cover to melt further.

Season with salt and pepper, garnish with chopped parsley or basil before serving.