Place a saucepan over medium heat. Add turkey drippings directly from the roasting pan. If using butter instead, allow it to melt completely until foamy but not browned.
Sprinkle flour evenly over the fat. Whisk continuously for 1–2 minutes until the mixture becomes smooth and slightly golden. This step is essential to remove the raw flour taste and create depth of flavor.
While whisking constantly, slowly pour in the warm turkey or chicken stock. Start with 2 cups and whisk until the gravy is smooth with no lumps. Keep whisking as the gravy begins to thicken.
Bring the gravy to a gentle simmer. Cook for 3–5 minutes, stirring often, until it reaches your preferred thickness. If it becomes too thick, add more stock a little at a time.
Season with salt and black pepper. Taste and adjust seasoning as needed. Add optional ingredients like cream or poultry seasoning if desired. Remove from heat once silky and smooth.