How to Make a Roux
Updated August 15, 2026
A roux is equal parts fat and flour by weight, cooked together before liquid joins. For a medium sauce, use 2 tablespoons each of butter and flour per cup of liquid: cook the raw smell off (2 minutes for white), whisk in liquid gradually, and simmer until thick. Longer cooking darkens the roux — more flavor, less thickening.
| Color | Cook time | Flavor | Classic use |
|---|---|---|---|
| White | 2–3 min | Neutral | Béchamel, mac and cheese, gravy |
| Blond | 5–8 min | Toasty | Velouté, pot pie, chowder |
| Brown | 15–30 min | Nutty | Espagnole, Cajun stews |
| Dark (chocolate) | 30–60 min | Deep, roasted | Gumbo — thickens only half as well |
The method that never lumps
Melt the butter over medium, whisk in the flour, and cook until it smells like pastry instead of raw flour. Then the anti-lump rule: cold (or room-temp) liquid into hot roux — or hot liquid into cold roux — whisking as you pour, gradually at first. Matching temperatures is what makes wallpaper paste. Simmer a few minutes after thickening; a sauce that never simmers still tastes of flour.
Thickness dial per cup of liquid: 1 tablespoon each of butter/flour for thin soup, 2 for a classic sauce, 3 for a croquette-grade binder.
Roux vs. the other thickeners
Roux thickens opaque, stable, and reheatable — the choice for gravies, cheese sauces, and anything made ahead. Cornstarch thickens glossy and clear in seconds but breaks down with long cooking and freezing (see the cornstarch vs. flour guide). Beurre manié — the same butter and flour kneaded raw and whisked into a finished simmering sauce — is roux's emergency-repair cousin.
Quick answers
- What's the ratio for a roux?
- Equal parts fat and flour. For sauces: 2 tablespoons of each per cup of liquid gives standard gravy thickness.
- Why is my roux-based sauce lumpy?
- Hot liquid hit hot roux all at once. Add liquid gradually while whisking with a temperature gap between them — and a blender rescues any sauce that's already lumped.
- Can I make a roux with oil?
- Yes — any fat works. Oil is traditional for dark Cajun roux because it survives long cooking; butter brings flavor to white sauces.