In a bowl, thoroughly mix the stuffing with the spinach, cranberries, a quarter of the chestnuts, half of the mushrooms, the foie gras cut into small cubes, the egg, salt and pepper.
To prepare the roast
Butterfly the turkey breast with a large knife to create a large cutlet.You can also ask your butcher to do this. Flatten it slightly with a rolling pin. Season with salt and pepper.
Place the sausage-shaped stuffing on one half and roll it up loosely.Tie it with kitchen twine.