Bring a large pot of salted water to a boil. Cook pasta until al dente. Drain and reserve ½ cup pasta water.
In a large skillet over medium heat, cook ground beef until browned. Drain excess fat if needed.
Add onion to the beef and cook until softened. Stir in garlic and cook for 30 seconds until fragrant.
Reduce heat to medium-low. Add heavy cream and milk, stirring gently until smooth.
Season with salt, pepper, and paprika. Simmer until slightly thickened.
Stir in Parmesan cheese until melted and creamy.
Add cooked pasta and toss to coat. Use reserved pasta water if needed to loosen sauce.
Remove from heat and garnish with parsley or red pepper flakes before serving.