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.
Add onion and cook until softened. Stir in garlic and cook until fragrant.
Reduce heat to medium-low. Add cream and milk, stirring gently until smooth.
Season with salt and pepper. Simmer until slightly thickened.
Stir in Parmesan cheese until melted and creamy.
Add cooked pasta and toss to coat. Use reserved pasta water to loosen sauce if needed.
Remove from heat. Garnish and serve warm.