Cook the shells according to package directions, drain, and set aside
In a large skillet, brown the ground beef over medium-high heat and add the Italian seasoning, dried parsley, red pepper flakes, and flour.
Stir in the beef broth, tomato sauce, and heavy cream. Bring to a boil, reduce the heat and simmer for 8 minutes until slightly thick. Season with salt and pepper.
Add the cooked pasta, remove from heat and mix in the cheddar and parmesan cheeses. Serve immediately with freshly chopped parsley on top.