In a 3 quart saucepan heat oil and butter. Add pancetta and cook for 6 to 8 minutes, or until most of the fat has be rendered. Then add carrots, celery, and onions and saute for 3 minutes. Now add the beef, salt and pepper to taste and cook until the beef is no longer pink. Add the milk and simmer gently, stirring occasionally, until the milk is completely evaporated. Add wine and simmer until evaporated.
Finally, add the tomatoes and simmer slowly, stirring occasionally, for 2 hours partially covered. It's important to reduce as slowly as possible. If sauce becomes dry, add 1/2 cup water whenever necessary. When almost ready to serve, bring a large pot of salted water to a boil. Cook the pasta until it is tender but still firm to the bite, 10 to 12 minutes. Drain, pat dry and return to the pot. Add your sauce to the past and toss to combine. Transfer to a serving bowl, and serve immediately. Top with freshly grated parmesan cheese if desired.