About 5 or 6 days before serving, bring the whole foie gras to room temperature for 30 minutes. It should soften just a small amount on the surface flesh.
Meanwhile, combine the wine, Port, chicken stock, sugar, salt, and peppercorns in a nonreactive 3-quart saucepan. Bring to a boil and simmer for 30 minutes. Let the liquid cool to between 120° and 125°F.
Generously season the foie gras with salt and pepper and submerge it, round smooth side down, in the warm poaching liquid. Cover with a sheet of parchment and poach the liver for 11 to 13 minutes, being careful to maintain the poaching liquid at no more than 125°F. At intervals of 4 minutes, use your hands to carefully turn the foie gras over while gently loosening the two lobes. The foie gras is fully cooked when it feels soft to the touch yet firm on the inside. Remove the saucepan from the heat and let the foie gras cool in the poaching liquid, covered with the sheet of parchment paper. When cool, refrigerate the foie gras in the liquid in the saucepan for 24 hours.
Remove the liver from the poaching liquid and pat dry with a soft towel. Tighten the towel and gently squeeze out any surface fat or liquid. Press the liver to shape it into an even loaf. Wrap in parchment paper, then plastic wrap, and finally a sheet of foil, and refrigerate for 4 to 5 days to allow the flavors to develop before serving.
To save the poaching liquid (la mère), strain it through cheesecloth and return to a clean saucepan. Bring to a boil, reduce the heat, and simmer for 10 minutes. Let cool, then refrigerate or freeze in a tightly covered container.
When ready to serve the foie gras, thinly slice the liver and arrange on plates. Garnish with the Salad of Bitter Greens with Truffle Vinaigrette, fleur de sel, and the grapes.
Rinse and dry the greens. Tear into bite-size pieces and put in a bowl.
Sprinkle the Champagne vinegar and truffle oil over the greens. Season lightly with salt and pepper. Toss to mix.
Sprinkle the pistachio nuts and chives on top.
Wine With Foie Gras Sauternes, the sweet white wine from Bordeaux, is the classic accompaniment to the fattened liver. Its sweetness complements the liver's richness, creating a velvet-smooth combination that should be slowly savored. Other sweet white wines, such as Monbazillac from the Pèrigord or any number of American sweet white wines, will also make a good marriage. Further possibilities include Champagne, a lightly chilled old Port, or even a light red Bordeaux.
