How to Thicken Sauce?

The quickest way to thicken a sauce is a cornstarch slurry: mix 1 tablespoon cornstarch with 1 tablespoon cold water per cup of sauce, stir it in, and simmer for 1–2 minutes until it thickens. But the best method depends on the sauce.

Method 1 — Cornstarch slurry (fastest, gluten-free)

Always mix cornstarch with cold liquid first — adding it dry creates lumps.

• Ratio: 1 tbsp cornstarch + 1 tbsp cold water per 1 cup of sauce for a moderate thickening.
• Stir into the simmering sauce and cook 1–2 minutes; it must reach a simmer to activate.
• Don't over-boil it afterwards, or it can thin back out.

Method 2 — Flour slurry or roux

• Slurry: 2 tbsp flour whisked into 4 tbsp cold water per cup of sauce. Simmer a few minutes longer than cornstarch to cook out the raw flour taste.
• Roux: cook equal parts butter and flour in a pan for 1–2 minutes, then whisk in your liquid. This is the classic base for gravies and cheese sauces, and it adds richness as well as body.

Method 3 — Reduction (best flavour, no additions)

Simmer the sauce uncovered over medium heat and let water evaporate. It takes longer but concentrates the flavour instead of diluting it. Ideal for pan sauces, tomato sauces, and reductions.

Method 4 — Beurre manié

Knead equal parts soft butter and flour into a paste and whisk small pieces into the simmering sauce. Great for finishing a sauce with gloss and body at the last minute.

Method 5 — Egg yolk

Whisk a yolk with a little of the hot sauce to temper it, then stir that back in over low heat. Never let it boil or it will scramble. Used for custards and rich cream sauces.

Method 6 — Purée or starchy vegetables

Blend some of the sauce's own vegetables, or add mashed potato, puréed beans, or a spoon of instant potato flakes. Adds body naturally.

Method 7 — Tomato paste

For tomato-based sauces, stirring in 1–2 tablespoons of tomato paste thickens and deepens the flavour at once.

Method 8 — Cheese, cream, or butter

Finely grated Parmesan or a splash of heavy cream thickens while enriching. Add cheese off the heat, a little at a time, so it doesn't split.

How to thicken sauce without cornstarch: use a roux, flour slurry, reduction, beurre manié, tomato paste, puréed vegetables, cream or cheese, or arrowroot/tapioca starch.

Best method by sauce type:

• Pasta / spaghetti sauce — reduction, tomato paste, or a ladle of starchy pasta water simmered in.
• Alfredo / cream sauce — Parmesan added off the heat, a roux, or gentle reduction. Avoid cornstarch, which can dull the texture.
• Tomato sauce — reduction plus tomato paste.
• Cheese sauce — build it on a roux from the start.
• Gravy — roux or a flour/cornstarch slurry.
• BBQ or teriyaki — cornstarch slurry, or simmer to reduce.
• Soup or stew — cornstarch slurry, or purée some of the vegetables.

Common mistakes: adding dry starch straight to hot liquid (lumps), not simmering long enough to activate the starch, and over-thickening — always add a little, wait a minute, then judge, because sauces also thicken as they cool.