Bring a large pot of salted water to a boil and cook the pasta until just al dente according to package directions. Drain and set aside.

In a large deep skillet or Dutch oven, heat the olive oil over medium heat. Add the onion and cook for 3 to 4 minutes until softened.

Add the ground beef and cook, breaking it up with a spoon, until browned and fully cooked. Drain excess fat if needed.

Stir in the garlic, chili powder, cumin, smoked paprika, salt, and black pepper. Cook for 30 seconds until fragrant.

Add the tomato paste, diced tomatoes, kidney beans, and beef broth. Stir well and simmer for 5 to 7 minutes until slightly thickened.

Reduce the heat to low. Add the butter and milk, then stir in the cheddar and Monterey Jack cheese a handful at a time until melted and smooth.

Fold the cooked pasta into the chili cheese sauce until evenly coated. Add a splash more broth or milk if the mixture is too thick.

Taste and adjust seasoning with more salt or pepper if needed. Serve hot, garnished with parsley or green onions if desired.