In a Dutch oven or large saucepan, heat the oil and butter over medium-high heat. Add the onion, celery and carrots; saute for 5 minutes or until the vegetables are tender.
Add the ground beef and sausage and cook for about 5 minutes (until browned), breaking up the meat into smaller pieces.
Add the milk and simmer for 8 minutes, until the milk is evaporated. Stir in the nutmeg, salt and pepper. Add the wine and simmer until the wine is evaporated. Add the tomatoes and their juices and bring to a boil. Reduce the heat to low and simmer, uncovered, for 3 hours, stirring occasionally. If the sauce becomes too dry, add water- 1 cup at a time.
At the end of the simmering time, prepare the pappardelle pasta according to package instructions.
Divide the pasta evenly between four serving bowls and top with the sauce. Sprinkle each serving with Parmesan cheese and garnish with fresh basil leaves (if using).