Brown the ground beef and diced onion in a large skillet over medium heat until the beef is fully cooked. Drain any excess grease.
Add the minced garlic and cook for about 30 seconds.
Transfer the beef mixture to the slow cooker.
Stir in the Rotel tomatoes, beef broth, cheddar cheese soup, cream cheese, chili powder, smoked paprika, garlic powder, onion powder, and black pepper.
Cover and cook on LOW for 3½ to 4 hours or HIGH for 2 hours.
About 30 minutes before serving, stir in the uncooked penne pasta.
Cover and continue cooking until the pasta is tender.
Add the shredded cheddar cheese and heavy cream, stirring until smooth and creamy.
Let the pasta rest for 5 minutes before serving.
Garnish with chopped parsley.