Shred the cheese and set it aside. Take the measured sour cream and milk out of the fridge and let it warm up to room temp.
In a large pot over medium heat, cook the ground beef and the onions until the ground beef is browned and crumbly. Add in the garlic and cook for another 1-2 minutes. Drain any excess grease and discard the grease.
Add in the tomato paste, diced tomatoes, the Worcestershire sauce and stir to combine.
Pour in the beef broth to the beef mixture and add in the uncooked macaroni. Stir lightly and bring to a simmer on medium heat.
Cover and simmer lightly for 10 minutes occasionally stirring. Pasta should be al dente. Reduce the heat to low.
Add in the room temperature sour cream and the milk. Stir gently to combine.
Gradually Add in 3 cups of the cheddar cheese, reserving 1/2 cup for topping. Stir gently until combined.
Dish into serving bowls, top with shredded cheddar cheese, bacon bits, parsley and serve.