Collect ingredients: pan drippings, flour, salt, black pepper, optional aromatics (onion/garlic), optional broth/stock or milk/cream
Make a roux: in a saucepan, melt butter (optional) and whisk in an equal amount of flour until smooth
Cook roux: cook 1–2 minutes, whisking, until lightly golden (for more color and flavor)
Add liquid: slowly whisk in warm broth/stock (or pan drippings plus broth) until smooth
Simmer: cook 3–8 minutes, whisking occasionally, until thickened
Season: add salt and black pepper to taste
Adjust consistency: thin with more broth; thicken by simmering longer or whisking in a slurry (1 tbsp flour or cornstarch mixed with 1–2 tbsp cold water)
Finish: whisk in pan drippings (if not already included) and strain if desired
Serve hot