In a large sauce pan, (a Dutch Oven pan works real well) add the olive oil, the carrots, celery and bay leaves. Let everything saute for about 5 minutes.
Add the onion and cook it until it becomes translucent. Add the beef and mix it well until it browns.
Add the rosemary and the wine and let it evaporate.
Add salt and pepper as desired.
Add 1/2 cup of beef broth, cover the pan and set flame to very low.
Every 15 minutes for the next 3 hours, give everything a stir and check for liquids. If the sauce is getting dry, add another 1/2 cup of broth.
After 3 hours, add all the remaining broth and continue to cook for another hour or so and contunue to stir every 15 minutes. At the end the sauce will be thick and... delicious!
Cook the Paccheri in salted water to Al Dente, drain and add to the sauce. Toss for 1-2 minutes and serve.