While the chickens are cooking, put the reserved fat in a nonstick skillet and heat it.
Strain and reserve the fat to use for cooking; also, spoon up or siphon off the fat from the roasting pan from time to time, adding it to the reserved fat.
Meanwhile, melt reserved fat in a saucepan over medium heat.
Dice the reserved fat, place in a small, heavy skillet and cook over medium heat until the pan is well filmed with fat.
Transfer the 3 tablespoons of reserved fat to a large, heavy skillet set over medium heat.
In large wide pot, heat the 2 tablespoons of reserved fat over medium heat.
Wipe out skillet and add reserved fat.
Wipe the pan clean and add the diced onion and the reserved fat to pan.
For the stuffing, heat two tablespoons of the reserved fat in a large non-stick frying pan and fry the onions for five minutes, or until softened and lightly browned, stirring occasionally.