There is a tremendous amount of discussion here on Chowhound about the "how to" behind Bolognese...I feel kind of guilty about adding another one, but... unless I somehow overlooked it, nobody nails the crux of the technique which is critical for making a great Bolognese.
That critical step is the slow rendering of all the fat out of the meat and the ensuing deep browning that occurs resultant of the maillard reaction between the natural sugars from the aromatics and tomato paste reacting with the meat proteins.
Start with the battuto of aromatics, a seasoned mirepoix and garlic is typical; (personally I skip the celery) sweat the vegetables down in butter- no oil because of the addition of milk later.
Once the soffritto is completely softened, and not brown whatsoever, only then do you add the meat which slowly renders...
What's critical here is to cook the meat long enough. This is where I feel many recipes, demonstrations, etc..fall short.
The meat needs to cook far longer than you'd normally think. All the water needs to be eliminated, and the end result is the meat and vegetables literally frying in the rendered fat at the bottom of the pan until deeply browned.
Only then is the paste added, and fried as well until caramelized; it should be a crackling and spitting affair.
Choice of meat is critical. There must be plenty of fat or it just won't work. My preference is a 70/30 beef (I use a minced wagyu or prime skirt), the addition of lamb, and a fatty pork.
When the base if fully browned, quite dark, then the milk is added. The temperature should be such that the milk incorporates and evaporates so quickly, that when mixed with the spoon, the meat & vegetable mixture lifts almost like a fast rising souffle. It will even have a cheesy aroma and flavor; an amazing transformation. It becomes creamy and velvet like. It should be soft.
In my experience this is what makes a Bolognese. The successful execution of this particular technique.
IMO you can take all the same ingredients, cook it as a sauce, but if you do not execute this technique mindfully it will not be a Bolognese.
Mario nails it in this video; I have not seen the proper technique filmed anywhere else: