Heat the olive oil in a Dutch oven over medium-high heat. Add the ground beef, break it apart, and let it sear to form a golden-brown crust. Cook until no pink remains. Remove the beef and set aside, leaving the fat in the pot.

Lower heat to medium. Add the diced onion to the beef fat and sauté for 4-5 minutes. Add garlic and cook for 1 minute. Melt the butter into the pot, then sprinkle in the flour. Whisk constantly for 2 minutes until a pale golden paste forms.

Gradually whisk in the beef broth, ensuring no lumps remain. Slowly pour in the whole milk. Bring the mixture to a gentle simmer (do not boil) and cook for 5-7 minutes until the liquid thickens and coats the back of a spoon.

In a separate pot of boiling salted water, cook the elbow macaroni until al dente according to package instructions. Drain well.

Remove the Dutch oven from the heat entirely. Gradually sprinkle in the freshly grated sharp cheddar cheese, stirring gently until completely melted into a thick orange-yellow broth. Fold in the cooked macaroni and browned beef crumbles.

Ladle the hot soup into bowls. Garnish generously with chopped fresh green parsley and tiny specks of black pepper. Serve immediately.