Use this rich meat sauce to make our Lasagna Bolognese.
Heat butter and oil in a large Dutch oven or heavy-bottom 6-quart pot over medium heat until butter is melted. Add onion, celery, and carrot; cook, stirring frequently, until vegetables are soft and light golden brown, 8 to 11 minutes.
Add ground chuck and pork to pot; stir, breaking up meat with a fork. Add salt, and continue cooking, stirring occasionally, until meat is cooked through but not browned, about 5 minutes more.
Gradually add milk; bring mixture to a simmer, then reduce heat to medium-low. Add nutmeg to taste, and gently simmer until milk has completely evaporated, about 20 minutes. (Any remaining liquid will be yellowish and clear.)
Add wine; simmer until liquid is reduced by half, about 15 minutes. Stir in stock; simmer until liquid is reduced by half, about 30 minutes. Add tomatoes and juice; simmer, stirring occasionally, until fat has risen to the top and sauce is thick and meaty, 60 to 70 minutes. Season with pepper. Let sauce cool slightly.
This sauce can be made 2 days ahead and stored in an airtight container in the refrigerator. Reheat before using.