Martha and Todd English prepare boneless turkey.
Bone the turkey: Place it on a work surface, breast side down. Slice skin along backbone from neck to tail. Cut and pull flesh and skin away from carcass. Cut flesh from saber-shaped bone near wing, and remove bone. Sever ball-and-socket wing joints so that they are separated from carcass but still attached to skin. Continue cutting breast meat away from bone up to the ridge of the breastbone. Turn turkey around, and repeat on other side. Pull gently to separate breastbone and carcass flesh (save carcass for homemade turkey stock). Cut off wing tip and middle section, leaving largest wing bone; save for stock. Holding outside of wing bone, cut through tendons; scrape meat from bone. Pull out bone, using knife to free it. Holding inside end of leg bone, cut through tendons attaching the flesh to the bone. Use knife to scrape meat from bone, pushing it away from end of bone. Cut bone free of skin. Cut out any sinews still remaining on leg. Repeat on other side, then push leg and wing skin side out. Butterfly breast so that meat completely covers skin. Cover with plastic wrap. Lightly pound meat until even.
Preheat oven to 375 degrees. Make the stuffing: Place a large skillet over medium heat; when it is hot, add 1 tablespoon olive oil. Add onion, garlic, 1 tablespoon chopped rosemary, sage, and mustard. Cook, stirring occasionally, until onion is soft and translucent but not brown, about 10 minutes. Transfer to a large bowl, and set aside to cool. Add the ground turkey and pork, breadcrumbs, eggs, cream, 1 1/2 teaspoons salt, and 1/4 teaspoon pepper to the bowl. Stir to combine.
Lay turkey breast on a work surface, skin side down, and season with 1 teaspoon salt, 1/2 teaspoon pepper, and remaining 2 tablespoons chopped rosemary. Place stuffing in the middle of the turkey. Roll turkey up to form a long tube; use toothpicks or wooden skewers to hold in place. Tie every 2 inches with kitchen twine. Drizzle with remaining 2 tablespoons olive oil. Season with remaining teaspoon salt and 1/2 teaspoon pepper. Tuck rosemary branches along the top of the roll under the twine. Place on roasting rack over a large pan.
Roast until an instant-read thermometer registers 150 degrees, 2 to 2 1/2 hours. Remove from oven. Brush with maple syrup. Return to oven, and roast until an instant-read thermometer registers 160 degrees to 165 degrees, about 20 minutes more.
Remove from oven, and let rest for 10 minutes. Transfer to a cutting board, remove twine, and cut crosswise into 1/2- to 1-inch-thick slices. Place slices on a platter, and garnish with watercress. Serve with cranberry compote.
If you do not want to bone the turkey yourself, you can have a butcher do it.