Blanch & peel half the tomatoes. Place in a slow cooker with half of the olive oil, the marjoram, rosemary, oregano, sugar, salt, sweet basil and garlic. Slow simmer for 24 to 48 hours or until the tomato solids are completely reduced. Blanch and peel the remaining tomatoes, remove the seeds and puree. Add to the slow cooker along with the tomato paste and continue to cook, very slowly, for another 24 hours. Saute the ground beef and add to the slow cooker along with the remainder of the olive oil. Continue cooking for at least half a day. During the last four hours of cooking, add the shredded parmesan cheese and blend in well. Add the mushrooms 15 minutes or so before serving. If you are planning meat balls, add them with the cheese and remove before serving. Serve the sauce over or alongside the pasta.