Recipe from New York Times Cooking

INGREDIENTS
1 stick butter
½ cup chopped onion
½ cup flour
Salt and pepper
4 to 5 cups rich stock, warmed
Turkey drippings and giblets (optional)
1 jalapeno, diced (optional)
½ – 1 tsp cayenne pepper (optional)

PREPARATION
Melt butter in a medium saucepan over medium heat, then add onions (and jalapeno, if you like it spicy).  Cook, stirring occasionally, until onions are translucent, about 5 minutes. Sprinkle the flour (and cayenne) on the onions, stirring constantly, and cook until flour is golden to brown. Adjust heat so mixture does not burn.
Gradually whisk in 4 cups stock until mixture thickens and is smooth. If it is too thick, add liquid. Cool, cover and chill.
When ready to serve, reheat mixture over low heat, stirring. Scrape bottom of turkey pan and add drippings or giblets to gravy. Taste and adjust seasoning, then serve.

Put this on top of Creamy Dreamy Mashed Potatoes