Bring a large pot of salted water to a boil. Add the elbow macaroni and cook according to package instructions until al dente, about 7-8 minutes. Drain and set aside.
While the pasta cooks, heat olive oil in a large skillet over medium-high heat. Add the chopped onion and sauté for 3-4 minutes until translucent.
Add the ground beef to the skillet with the onions. Cook, breaking it up with a spoon, until browned and cooked through, about 6-8 minutes. Drain excess fat if necessary.
Add the minced garlic to the beef mixture and cook for 1 minute until fragrant. Remove the beef mixture from the skillet and set aside.
In the same skillet, reduce heat to medium and add the flour. Stir constantly for 1-2 minutes to form a roux, ensuring it does not brown.
Gradually whisk in the milk, continuing to whisk until the sauce thickens, about 4-5 minutes.
Remove the skillet from heat and stir in the shredded cheddar, mozzarella, Parmesan cheese, Dijon mustard, salt, black pepper, and smoked paprika until smooth and creamy.
Return the cooked ground beef and onions to the cheese sauce and stir to combine.
Add the drained macaroni to the skillet and mix thoroughly to coat the pasta evenly with the beef and cheese sauce.
Serve hot, garnished with additional Parmesan cheese if desired.