In bowl of food processor fitted with knife blade attachment, pulse celery, carrots and onion until very finely chopped.

Heat oil in large pot over medium heat. Break ground beef into about 8 chunks and add to pot. Season with salt. Cook, stirring occasionally but not breaking up meat, 6 to 8 minutes or until outside of beef chunks are browned. Using slotted spoon, transfer beef to medium bowl.

Add celery mixture to pot and cook 10 to 15 minutes or until all moisture has evaporated and vegetables begin to lightly stick to bottom of pot, stirring occasionally.

Stir in wine and reserved beef. Reduce heat to medium-low and cook 8 to 10 minutes or until wine is evaporated, using spoon to break beef into small bits as it cooks.

Add tomato paste, bay leaf and thyme and cook 5 minutes or until tomato paste is slightly browned, continuing to break beef up as it cooks.

Stir in water, milk, and a pinch of salt. Reduce heat to low and cook, uncovered, 2 hours or until mixture has reduced to a sauce consistency and meat is very tender, stirring about every 30 minutes. Remove and discard bay leaf and thyme sprig. Taste sauce and season with additional salt if necessary.

Heat large pot of salted water to boiling over high heat. Add rigatoni and cook for 2 minutes less than package directions for al dente.

Reserve 1 cup pasta cooking water. Drain pasta and transfer to pot with bolognese. Add 1/2 cup reserved pasta cooking water. Increase heat to medium, and cook, while stirring pasta and sauce together, 2 minutes or until pasta is al dente and everything is combined. Add additional pasta water if necessary, to keep things saucy!

Serve topped with Parmesan cheese and parsley.