While your chicken rests, add chicken stock and a touch of butter to the skimmed pan drippings to create this delicious pan gravy.
While the chicken rests, pour the pan drippings into a shallow bowl or a fat separator, leaving the onions in the pan. Using a fat separator or large spoon, skim off and discard as much of the fat as possible.
Pour the remaining drippings and juices back into the roasting pan. Place pan over medium-high heat, and cook for about 1 minute. Add chicken stock, and raise the heat to high. Using a wooden spoon, deglaze the pan by stirring up any brown bits so that they combine with the stock; these brown bits add flavor to the gravy. Cook until the liquid is reduced by half, about 4 minutes.
Strain into a small bowl, pressing down on the onions with the back of a spoon to extract any remaining liquid; discard the onions. Stir in butter until it is fully incorporated. Serve immediately.