Carefully add about a pint of broth or stock, whisking into the roux. Stand back as the hot skillet may steam from the cold liquid (as an additional step, preheat your broth or stock before adding it to the roux). After roux is incorporated into the liquid, return the skillet to medium heat. Whisk occasionally.
Remove from heat and whisk in broth or stock.
Continue to whisk over medium heat to blend together roux and broth.
Allow the gravy to thicken and reduce, then lower the heat. If using the gravy to reheat cooked food such as leftover turkey, place the food in the gravy and let it cook gently until warmed.
Optional: Use gravy to gently reheat cooked meat or poultry.
To serve, remove all food from the gravy and plate for serving. Remove skillet from heat. Stir in one pat (approx. 1 Tbsp.) butter to finish the gravy. Pour into gravy bowl to serve.