Let the foie gras stand at room temperature for about 1 hour.
Devein the foie gras: Gently pull apart the 2 lobes. Make a shallow incision in the smaller lobe at the point where it was attached to the larger lobe. Using tweezers or the tip of a thin-bladed knife, carefull pull out all visible veins.
Sprinkle both sides of the foie gras with salt and pepper. Place in a glass dish. Add the ice cider. Cover and refrigirate for 24 hours.
Remove the dish from the refrigerator and let stand at room temperature for 30 minutes. Drain, reserving the marinade.
Wrap the foie gras in a clean tea towel or piece of cheesecloth. Shape it into a cylinder 3 inches (7.5 cm) in diameter. then wrap the tea towel in a long sheet of plastic wrap. Seal tighly by twisting and tying both ends.
In a saucepan, combine the marinade and enough broth to cover the foie gras. Clip a thermometer to the side of the saucepan and heat until the temperature reaches 140°F (60°C). Place the wrapped foie gras in the liquid and poach for 25 minutes, maintaining the temperature at 140°F (60°C).
Remove the foie gras and refrigerate for 24 hours.
Carefully unwrap the foie gras. Slice and serve with slices of toasted brioche and fleur de sel, or use a portion for the Roast Chicken with Foie Gras (see recipe).