Slice the onions and fry them in a little butter till well browned. Remove them from the butter and cook the rice in this same butter till it has absorbed it completely. Add the seasoning and cover with the stock. Cover the saucepan and simmer till the rice begins to soften and swell. Stuff the chicken with the rice, sew up carefully and wrap up the chicken completely in a casing of paste made with flour and water. Tie in a cloth and boil for 1 to 2 hours, according to the weight of the chicken.