Hearty Spaghetti Sauce

Directions

1. Melt butter in a large saucepan over medium heat. Add celery, carrots, onion, garlic, and salt; cook stirring occasionally until tender, about 5 min.
2. Remove sausages from casings and add to pan along with ground beef. Use a fork to break up meat; stir continously over medium heat until no longer pink, about 5 min. Add milk.
3. Gently boil, uncovered, stiring occasionally for 5 min. 
4. Add tomatoes, mashing with a potato masher to break them up. Add parsley and chili flakes, if using mild sausage.
5. Simmer, uncovered, stirring occasionally 30 min or until thickness desired.