Reserve capon offal.
Peel onion and cut in two part. Peel carrot and slice.
Bring to a boil in a very very large casserole dish enough water with onion, carrot and salt, in order to cover half of the capon. My casserole dish wasn't big enough to cover it enterely.
Add capon and poach, meaning cook it 40 minutes or 20 minutes on each side, if like me your casserole isn't big enought to cover entirely your poultry.
Remove from water and leave to cool capon.
In the meantime, prepare stuffing.
In a pan, fry offal with 2 shallots peeled and sliced. Chop finely and reserve.
Dice bread and soak into milk.
Dice foie gras, after removing vein.
Mix bread, foie gras and offal in a large recipient. Season with salt and pepper. Stuff your capon.
Sew the hole with cooking string and needle (or toothpick) so the stuffing doesn't leave your capon.
Preheat oven to 200°C.
Cook for 1 hour and reduce to 150°C for approximately 2 hours.