In a medium saucepan, melt the butter over medium heat. Whisk in the flour to make a roux. Cook, stirring constantly, for about 2–3 minutes until it smells nutty — this cooks out that raw flour taste.
Gradually whisk in warm stock, a little at a time, to prevent lumps.Bring to a gentle simmer, whisking until it thickens to your liking — about 5–7 minutes.
Season well with salt and pepper. Add a splash of wine or vinegar if you want to brighten the flavor.
Keep warm until serving. Stir before pouring over everything.If you have your own "drippings" use 2 tablespoons of fat from drippings. (Make and two tablespoons of flour and 16 oz of stock. And follow the directions above.