Turkey:
Preheat oven to 325°F.
Heat evoo in a large Dutch oven over medium heat. Brown turkey legs and thighs, cooking for 3 to 5 minutes per side, until skin is crisp and golden brown. Transfer to a plate.
Add onion, celery, and carrots to the Dutch oven, and cook for 7 to 10 minutes, or until browned. Add turkey legs and thighs, garlic, mushrooms, bouquet garni, wine, and broth back to the pot. Cover and braise for 1 hour.
Uncover and continue cooking for 1 hour more, or until legs are tender and meat is almost falling off the bone.
Transfer legs and thighs to a platter. Skim off and discard fat from braising liquid. Spoon remaining juices over legs. Top with some of the Gremolata, and serve with additional Gremolata on the side.
Gremolata:
Pulse parsley, garlic, zest and orange juice, zest and lemon juice, evoo, and pumpkin seeds until it forms a coarse paste.
Spoon over turkey legs. Transfer remaining to a small bowl and serve alongside turkey.