Cut the carrots, celery and onion into medium-sized pieces (no need to be precise- they will go into the food processor)
Place the carrots, celery and onion in a large food processor. If they don't all fit, you may need to work in batches.
Pulse in the food processor until finely chopped.
To a large heavy bottom pot, over medium heat, add the olive oil. Once warm, add the pancetta.
Let the pancetta cook until golden, about 5 minutes. Add the minced celery, carrot and onion.
Let them cook until tender, about 5-10 minutes.
Add the ground beef. Let it cook until browned. This can take awhile - about 10-20 minutes. Ensure to let it brown, as this is where a lot of the flavor will come from.
Add the white wine and scrape the bottom of the pot to lift off any brown bits - this will help build flavor.
Add the jars of crushed strained tomatoes. Give everything a big stir. Let the sauce come to a boil. Turn the heat down to the lowest setting.
Partially cover the pot with a lid and let the sauce cook down - for about 3 hours. Add salt if necessary. But the pancetta is already very salty so you may not need to add any salt.
If sauce dries up too much while it's cooking, add a few ladles of unsalted vegetable broth.
Cook the tagliatelle and add them to sauce. Mix the tagliatelle with the sauce with tongs.
Plate and top with parmigiano reggiano.