Heat a large pot with 2 tablespoons of olive oil over low heat. Add in the carrot, celery, onion, bay leaf and cinnamon, and cook, stirring often for about 5 minutes, until the veggies have softened.
Add the finely chopped duck meat and continue to cook, stirring often, until it's browned.
Pour in the wine and allow to evaporate, about 5 minutes.
Add in the tomatoes (if using), followed by half of the stock. Reduce heat to very low, partially cover the pot with a lid, then slowly cook the duck ragu' for at least 1½ hours.
Stir the sauce occasionally, and if you see it's drying out, pour in a bit of stock. During the last half an hour of cooking, pour in the milk or orange juice.
The sauce is ready when it reaches a dense and rich texture. If it's still too runny, let it cook a little more .
Serve with your favorite pasta (pappardelle, bigoli, rigatoni, etc), top with Parmigiano cheese and serve.