To bone, place duck breast up and remove the flap of skin covering the wishbone. Scrape along the wishbone with the back of a paring knife to expose the bone. Reach in with index finger and thumb to remove the wishbone by pulling it out, being careful not to tear the meat.
Make incision along the breastbone and from breastbone down to rib cage. Follow rib cage to thigh and wing joints and carefully cut through thigh and wing joints leaving wing attached to breast. Separate the breast from the thigh and leg.
Remove the wing at the middle joint and cut the end of the attached wing bone square. Push the meat on the wing down toward the breast, cleaning the bone with a paring knife. Push the meat on the bones of the thigh and leg, leaving the leg bone attached to the meat at the drum end. Square off the end of the drumstick with a French knife. Remove the thigh and the thighbone. Repeat for other half of duck. (Note: you may use boneless duck breasts if limited on time.)
Lay breasts skin side down, clean the excess skin, and shape into teardrops with a boning knife. From the thick end, pierce the breast directly beneath the skin, straight in to the tip of the breast, making a pocket. Be careful not to poke through the flesh while making pocket. Pocket should extend the length of the breast.
In a saucepan, saute the leeks in the butter until tender. Add the herbs and carefully deglaze the pan with apple brandy. Add 1 ounce of cream, reduce until thickened, and cool.
In a meat grinder, grind the thigh meat and liver through the fine die. Using a food processor, process until smooth. Add remaining cream, and mix well. Add leek mixture, and season, to taste.
Using a pastry bag, pipe approximately 2 tablespoons of forcemeat into each duck breast pocket. Plug the end of the pocket with the tender.
Preheat the oven to 400 degrees F.
Brown duck breast in a heavy skillet over medium-high heat, skin-side down, until golden brown, about 5 minutes. Turn duck breast over, place in the oven, and cook until desired temperature is reached.