Add the onion, celery and carrots to the bowl of a food processor fitted with the blade attachment. Pulse until finely chopped and set aside. If you do not have a food processor then finely chop the vegetables by hand.
Heat a large heavy bottomed pot over medium-high heat. Cook the beef, pork, veal and sausages in small batches in the sauté pan. After each batch is browned, set it aside in a large bowl.
Return pot to medium heat, add the olive oil and heat through. Sauté the onion, celery, and carrots in olive oil until very soft and slightly light brown.
Stir in the garlic, oregano and basil, and continue to sauté 3 to 5 minutes. Add the red wine and reduce until the vegetables are almost dry, about 15 minutes.
Stir in the sautéed meat. Add the cans of tomatoes with their liquid and 1 cup of water, stirring to combine.
Cook over medium to medium-low heat for 3 to 6 hours and stir frequently so that it does not burn. Add more water as needed if the sauce becomes too dry.
With about 5 minutes left of cooking, stir in the cream followed by the Parmesan cheese. Season to taste with salt and pepper. The sauce may need a little sugar to adjust the acidity.
Bring a large pot of water to a boil; add the salt and bring back to a boil. Pour in the pasta and cook, stirring occasionally, until al dente, about 10 minutes.
Drain and return the pasta to the pot. Ladle in the enough of the Bolognese to coat the pasta. Divide pasta into warmed bowls and serve topped with additional Parmesan cheese.
Notes
Make the sauce ahead of time and refrigerate or freeze until ready to use (up to 3 months in the freezer). Add to resealable or airtight plastic bags and store flat on a baking sheet until frozen