1 large celery root about 2 lbs, peeled and cut into ½ inch dice
2 large russet potatoes, peeled and cut into ½ inch dice
About 3 cups chicken stock
4 tablespoons butter
2 tablespoons chopped chives
2 large fresh duck breasts
2 ounces black truffle (preferably two, one-ounce truffles)
3 shallots, sliced thin
2 tablespoons rendered duck fat
1 teaspoon sugar
1/3 cup cognac or brandy
2 cups rich chicken or duck stock
8 ounces foie gras cubes or scraps, at room temperature
salt and pepper
four, 2-oz slices of foie gras (optional)
First, prepare the celery root puree. Put diced celery root and potatoes in a large pot and cover with chicken stock. Cover pot and boil for 15 minutes or until vegetables are tender. Add additional stock if needed. Drain the celery root and potatoes and pass them through a ricer, or blend in a food processor. Return the puree to the pot, add butter and salt and pepper to taste. Keep warm over low heat, or reheat prior to serving.
Slice 1 ½ ounces black truffle, into approximately 36 slices. Finely chop the remaining ½ ounce.
Trim duck breasts of any sinew, leaving fatty skin totally in tact. Using your fingers, pull skin away from the breast meat from each side of duck breast, leaving about a ½ inch strip of fat attached lengthwise to meat in center of breast. Tuck a row of black truffle slices under the flaps of duck skin on each side of the two duck breasts (use 24 of the 36 truffle slices). Press skin flaps down over truffles to cover them completely. Score the top of duck skin in a crosshatch pattern, without cutting into the meat. Refrigerate for at least four hours and up to one day.
Remove duck breasts from refrigerator and let stand 30 minutes at room temperature. Preheat oven to 350°F. Carefully lift duck breast skin flaps and sprinkle salt and pepper on the truffles and on the meat side. Heat a large ovenproof skillet over medium high heat. Place duck breasts, skin side down, in the skillet. Cook the duck breasts until the skin is deep golden and crisp, about 10 minutes. Drain some of duck fat as it renders and set aside (it’s best to prevent the truffles from being directly exposed to the sizzling duck fat. Place the skillet with the duck breasts in oven for 5 – 8 minutes, or just until duck is cooked to desired doneness. Remove duck breasts from skillet, cover and let them rest on a platter for 10 minutes.
While the duck breasts are cooking on the stove, saute the shallots in reserved duck fat with the sugar until caramelized. Deglaze the pan with brandy or cognac and reduce the liquid to about 2 tablespoons. Add the chicken or duck stock and continue cooking until the liquid is reduced to about one cup. Pour the hot sauce into a blender and immediately add cubes of raw foie gras while the blender is still running. Add the chopped truffle and blend lightly. Season with salt and pepper if needed. Leave the foie gras sauce in the blender to keep it warm.
To serve, slice the duck breasts and place 4 – 6 slices on each plate, next to a mound of celery root puree, and any vegetable you choose to have with this dish. Pour foie gras truffle sauce around the duck breast slices and celery root puree. Garnish the celery root puree with chopped chives, and place three slices of black truffle on the duck and foie gras truffle sauce. If desired, add a 2-ounce slice of seared foie gras to each plate.