How to Thicken a Sauce: 8 Methods That Work
Quick steps (10 min)
You need: whisk, small bowl, saucepan
You can thicken a sauce by reducing it (simmering off water), adding a starch like cornstarch or flour, or enriching it with an emulsion of butter, cream, or egg yolk. The best method depends on the sauce: a quick cornstarch slurry for a stir-fry, a roux for gravy, reduction and butter for a pan sauce.
The three ways sauces get thick
Every thickening method works by one of three mechanisms:
- Removing water. Reduction concentrates dissolved solids like gelatin, sugar, and proteins until the liquid gets viscous. It also concentrates flavour and salt.
- Adding starch. Starch granules swell and release long molecules when heated in liquid, tangling into a thick network. This is starch gelatinization. Different starches gelatinize at different temperatures and give different textures.
- Adding fat or protein. Cold butter forms an emulsion of tiny fat droplets; egg yolks thicken as their proteins set; cream reduces into a rich, coating sauce.
Method comparison
| Thickener | Amount per 250 mL / 1 cup | Look | Best for | Watch out for |
|---|---|---|---|---|
| Reduction | Simmer to half or less | Glossy if gelatin-rich | Pan sauces, jus, wine sauces | Concentrates salt |
| Cornstarch slurry | 1 tbsp (8 g) | Clear, glossy | Stir-fries, fruit sauces, gravy | Breaks if over-boiled or frozen |
| Arrowroot / tapioca slurry | 1–1.5 tbsp | Very clear | Acidic or fruit sauces | Goes stringy if overheated |
| Roux | 2 tbsp fat + 2 tbsp flour | Opaque | Gravy, béchamel, gumbo | Must be cooked before liquid |
| Beurre manié | 1–2 tbsp | Opaque, silky | Last-minute fixes, stews | Needs 3–5 minutes simmering |
| Cold butter | 2–3 tbsp | Glossy, creamy | Pan sauces, beurre blanc | Breaks if boiled |
| Egg yolk liaison | 1 yolk + 60 mL cream | Velvety | Velouté, blanquette | Curdles above about 80 °C / 175 °F |
| Purée | A few tablespoons | Rustic | Soups, curries, stews | Changes flavour |
Cornstarch has roughly twice the thickening power of flour, so 1 tablespoon cornstarch does about what 2 tablespoons flour do.
Steps
- Decide what the sauce needs. If it's thin but flavourful, add starch. If it's thin and bland, reduce first. If it's nearly there and needs richness, finish with butter or yolk.
- To reduce, simmer uncovered over medium to medium-high heat, stirring occasionally, until the sauce coats the back of a spoon and a finger drawn through it leaves a clean line (nappe).
- To make a slurry, stir 1 tablespoon cornstarch into 2 tablespoons cold water until smooth. Starch dissolved in hot liquid clumps instantly, so the water must be cold.
- Whisk the slurry in gradually, about a third at a time, into the simmering sauce. Cornstarch gelatinizes around 62–72 °C / 144–162 °F, but it reaches full thickness close to the boil.
- Simmer 1–2 minutes, until the sauce turns glossy and loses any cloudy, starchy look. Don't boil hard for long; cornstarch can thin again.
- To use flour instead, knead equal weights of soft butter and flour into a paste (beurre manié). Whisk in pea-sized pieces, then simmer 3–5 minutes to cook out the raw flour taste.
- To enrich, take the pan off the heat. Whisk in cold butter a cube at a time, or stir in heavy cream and simmer gently. For an egg yolk liaison, whisk a yolk with 60 mL cream, temper it with a ladle of hot sauce, then stir it back in and heat gently without boiling.
- Taste and adjust. Thickeners dull flavour slightly, so you'll often need a pinch more salt or a squeeze of acid.
Quick fixes by sauce
- Gravy: Cornstarch slurry, beurre manié, or a roux made in the drippings.
- Tomato pasta sauce: Simmer uncovered longer, or stir in 1–2 tablespoons tomato paste. A splash of starchy pasta water helps sauce cling to the noodles.
- Curry or stew: Simmer uncovered, or mash or blend some of the potatoes, lentils, or vegetables.
- Cream sauce: Reduce gently, or add grated Parmesan off the heat.
- Stir-fry sauce: Cornstarch slurry, added at the very end.
- Fruit sauce or pie filling: Cornstarch, arrowroot, or tapioca for clarity. Arrowroot holds up best with acid.
- Gluten-free or low-carb: A tiny pinch of xanthan gum, about 1/8 teaspoon per 250 mL, whisked or blended in.
Common mistakes and fixes
Lumps. Dry starch went straight into hot liquid. Whisk hard or strain through a sieve; next time, always make a slurry or paste first.
Sauce tastes floury. Flour wasn't cooked enough. Simmer at least 3–5 more minutes.
Sauce got gloopy or gummy. Too much starch. Whisk in more stock or water.
Sauce thinned after being thick. Cornstarch broke down from overcooking, hard stirring, or acid. Add a little more fresh slurry at the end.
Butter sauce split. It got too hot. Off the heat, whisk in a spoonful of cold water or cream.
Too salty after reducing. Salt concentrates as water evaporates. Season at the end, and use low-sodium stock for reduced sauces.
Out of cornstarch? See the cornstarch substitute guide for ratios with flour, arrowroot, potato starch, and tapioca.
Questions
How much cornstarch do I need to thicken a sauce?
About 1 tablespoon (8 g) of cornstarch thickens 250 mL (1 cup) of liquid to a medium sauce. Always mix it with twice as much cold water first, then whisk it into simmering liquid.
How do you thicken a sauce without cornstarch or flour?
Reduce it by simmering, blend in some of the cooked vegetables, whisk in cold butter or a tempered egg yolk, or add tomato paste, grated cheese, or a spoonful of nut butter, depending on the sauce.
Why did my cornstarch sauce get thin again?
Cornstarch thins if it's boiled too long, stirred vigorously after setting, or combined with strong acid. It can also break down if the sauce is frozen and thawed. Add it near the end and simmer just until thick.
Should I use flour or cornstarch to thicken a sauce?
Flour gives an opaque, matte sauce and handles long simmering and freezing well, so it suits gravies and stews. Cornstarch gives a clear, glossy finish and twice the thickening power, so it suits stir-fries and fruit sauces.
Why does a sauce thicken as it cools?
Starch networks and gelatin both firm up as temperature drops. Aim for a slightly looser consistency in the pan than you want on the plate.