In a large skillet, brown the ground beef over medium heat until fully cooked. Drain excess grease.
Transfer the beef to a slow cooker and add beef broth, heavy cream, garlic, onion powder, salt, and pepper.
Stir everything together, cover, and cook on low for 4 hours.
Add uncooked penne pasta to the slow cooker, stir, and cook for an additional 30 minutes until pasta is tender.
Stir in butter and parmesan cheese until melted and creamy.
Serve hot, garnished with fresh parsley.