Head the oil in a large Dutch Oven over medium heat. Add the lamb and cook it until it's brown, using a wooden spoon to gently chop up the mince.
Slide the meat to one side, then add the onion, celery and carrot to the other side, sweating the vegetables for about 5 minutes until they're soft. Combine the meat and vegetables together.
Add the garlic, tomato paste and salt and pepper and cook for a further 5 minutes until the liquid has almost evaporated.
Add the red wine, use your spoon to gently scrape the bottom of your pot to release all the good bits at the bottom. (this process is called deglazing)
Cook for 5 minutes until the sauce thickens.
Add the bay leaves, thyme and rosemary and half the chicken stock.
Add the tomatoes and stir. Bring to the boil, then reduce heat to simmer the sauce for 15 minutes.
Add the remaning chicken stock, and gently simmer, uncovered for 2 - 2 ½ hours until the sauce is really thick and most of the liquid has evaporated.
Remove the bay leaves and rosemary and thyme twigs.
Season with salt and pepper to taste.
Meanwhile cook your papardelle according to packet instructions.
Plate your pasta and add a good spoonful of the ragu onto the pasta. Sprinkle over some parmesan cheese and a sprig of thyme.