Heat large pot over medium heat.
Add duck fat or olive oil and bay leaf.
Add finely diced carrot celery and onion when the oil is hot. Season with salt. Cook until soft.
Move the veg to the side of the pot. Place duck leg skin side down into the bottom of the bare pot. Sear until golden brown. About 10 minutes.
Flip the legs and add wine. Simmer until the alcohol is cooked off (a couple of minutes), add stock or water, and cook uncovered until reduced by about half. Stir in the passata and tomato paste.
Move duck legs to coat all sides and leave skin side up. Cook on low heat until meat is tender. Approx 2 hours.
Remove duck legs from pot and allow to cool. Using tongs, remove duck meat from bones and any skin that did not render off. Shred duck meat using forks. Add meat back into the pot. Season with salt and pepper to taste. Skim off any excess fat from the top using a ladle.
Bring a separate large pot of salted water to a boil. Cook pici until Al dente, approx 9 minutes.
Reserve a cup or two of pasta water before draining. Add cooked pasta to the sauce and about a half cup of pasta water and stir to emulsion the water with the sauce. Add more pasta water if needed to thin the sauce out to preference. Serve with grated Parmesan