Heat olive oil in a large heavy-bottomed pot over medium-high heat. Add onions, celery, and carrots. Sauté until soft, 10-12 minutes (longer if you want).
Add beef and veal (ground meat of choice)- sauté, breaking up with the back of a spoon, until browned, about 15 minutes.
Add tomatoes; boil for 2 minutes, stirring often and scraping up browned bits. If using whole tomatoes use the back of a wooden spoon, or a spatula, to crush them into small pieces.
Reduce heat to low heat and gently simmer, stirring occasionally, until flavors meld, 40 minutes. Season with salt and pepper.
Boil pasta according to directions. When pasta is done cooking place it in a large serving dish and toss the ragu sauce until it coats the pasta completely.
Top with plenty of freshly grated Parmigiano cheese and sprinkle with parsley, if desired. Enjoy hot!
