In a large pot over medium heat, brown the ground beef until it's fully cooked. Drain any excess fat.
Add the chopped onion and minced garlic to the pot, sautéing until the onion is translucent and fragrant, about 3-4 minutes.
Stir in the Italian seasoning and red pepper flakes (if using) until combined.
Pour in the beef broth and bring the mixture to a boil.
Once boiling, add the shell pasta and reduce the heat to a simmer. Cook for about 8-10 minutes, or until the pasta is al dente, stirring occasionally.
Stir in the heavy cream, shredded cheddar cheese, and frozen peas. Continue cooking until the cheese has melted and the mixture is creamy, about 2-3 minutes.
Season with salt and pepper to taste.
Remove from heat and let it sit for a few minutes to thicken slightly before serving.
Notes
Serve in deep bowls, garnished with chopped fresh parsley and an extra sprinkle of cheese on top for a pop of color.