In a large pot, bring salted water to a boil. Cook the elbow macaroni according to the package instructions until al dente. Drain the cooked macaroni and set it aside.
Heat a Dutch oven over medium heat, then add the ground beef. Cook the ground beef, breaking it up into crumbles as you go, until it’s almost browned, about 6-7 minutes. Drain away any excess fat.
Add the chopped onion and sliced mushrooms to the pot with the ground beef, and continue to cook until the beef is no longer pink and the onion is softened, about 3-4 minutes. Add the minced garlic and cook until aromatic, about 1 more minute.
To the same pot, add cheese (leaving some for garnish), milk, sour cream, sauce, Dijon mustard, Worcestershire sauce, salt, black pepper, and paprika. Stir well to combine. Once combined, add the cooked elbow macaroni, and mix again until it’s evenly coated.
Bring the mixture to a gentle simmer over low heat, stirring occasionally, until the cheese has fully melted and the sauce is creamy, about 10-15 minutes. If the mixture seems too thick, you can add a splash of milk or extra sour cream to adjust the consistency.
Remove the pot from heat, sprinkle with the remaining shredded cheese and let it rest for 5 minutes before serving.
