Make a soffrito first- basis of many Italian recipes
That is finally cut onion, carrot and celery and gently, very gently cook for at least 10 mins , maybe even 15 mins before you do anything else. The veg should be very soft, a pale golden but not obviously caramelised, (Note that many Italians would say don’t need garlic and onion- but I do add minced garlic to this mix at the very end, not at start as it will burn and be bitter)
Sauté off the lardons (do not throw the fat, this is important to the flavour) , then add mince and sauté on high till brown on outside but still pink inside. ( if you want to save some time, otherwise remove soffrito when done and add to pan). Then add about a glass of milk
Add back everything togther, add a lot of red wine, oregano, bay leaves (essential) pepper and tinned tomatoes. Add a good stock (beef) and maybe if you have a few dried mushrooms and their soaking water for a bit of Unami kick.
Cook for a LONG time on slow gentle heat (eg. 1.5-2 hours) A really long time. I use a pressure cooker to speed it up.
Add chopped mushrooms , cook at higher heat to reduce the liquid to nearly nothing. It should be a fairly dry sauce. People insist on having bolognaise with a watery gravy around it.
Season well at the end.