A slurry is a simple mixture of a cold liquid and a starch—usually cornstarch, flour, or arrowroot—used to thicken soups, gravies, sauces, and stir-fries without forming lumps. It works because the cold liquid separates the starch granules so they disperse evenly into hot liquid, where they swell and thicken. This technique is essential for achieving a silky, glossy texture in everything from Chinese velveting sauces to classic French pan gravies.
Ingredients
- 1 tablespoon (8 g) cornstarch (or all-purpose flour, arrowroot, or potato starch)
- 2 tablespoons (30 ml) cold water, broth, wine, or other cold liquid (use 2 tbsp / 30 ml for cornstarch; 3 tbsp / 45 ml for flour)
This makes enough to thicken about 1 cup (240 ml) of liquid. For a larger batch, use a 1:2 ratio of starch to cold liquid by volume (e.g., 2 tbsp cornstarch to 4 tbsp cold liquid).
Instructions
- Measure the starch. Place the cornstarch (or your chosen starch) in a small bowl. Use the exact amount your recipe calls for—usually 1 tablespoon per cup of liquid you want to thicken.
- Add cold liquid. Pour the cold water (or other cold liquid) over the starch. Use 2 tablespoons of liquid for every 1 tablespoon of cornstarch. If using flour, increase the liquid to 3 tablespoons per 1 tablespoon of flour.
- Whisk until smooth. Whisk vigorously with a fork or small whisk until no dry lumps remain. The mixture should look like heavy cream. If you see lumps, keep whisking—they will break up with a few more strokes.
- Add to hot liquid. Slowly pour the slurry into your hot sauce, soup, or gravy while stirring constantly. Make sure the liquid is simmering (not just warm) for the starch to activate.
- Simmer and stir. Cook for 1–2 minutes, stirring continuously, until the liquid thickens and becomes glossy. The mixture will thicken more as it cools, so do not over-thicken at this stage.
- Check consistency. If the sauce is still too thin, repeat with a fresh slurry (using 1 teaspoon of starch at a time) and simmer again. If it is too thick, whisk in a little hot liquid to thin it.
Tips
- Always use cold liquid. Hot liquid will cause the starch to clump instantly. Cold liquid ensures a smooth dispersion.
- Do not boil vigorously for too long. Cornstarch-thickened mixtures can break down if boiled for more than a few minutes. Simmer gently just until thickened.
- Flour slurry needs more liquid and longer cooking. Use 3 parts liquid to 1 part flour, and simmer for at least 2–3 minutes to cook out the raw flour taste. Cornstarch needs only 1–2 minutes and gives a clearer, glossier finish.
- Acidic ingredients can affect thickening. If your sauce has a lot of vinegar or tomatoes, use arrowroot or cornstarch, as flour may break down in acidic conditions.
Serving Suggestions
Use a slurry to thicken beef stew, chicken gravy, fruit pie fillings, sweet-and-sour sauce, or a simple pan sauce after searing meat. It is also the key to a glossy stir-fry sauce—mix soy sauce, sugar, and a slurry, then add to the wok at the end of cooking.
Variations
- Arrowroot slurry: Use 1 tablespoon arrowroot to 2 tablespoons cold liquid. It thickens at a lower temperature and produces a very clear, shiny glaze—ideal for fruit sauces.
- Potato starch slurry: Use 1 tablespoon potato starch to 2 tablespoons cold liquid. It gives a soft, chewy texture, great for Asian dishes, but do not over-stir or it can become gluey.
- Flour slurry: Use 1 tablespoon all-purpose flour to 3 tablespoons cold liquid. It is less glossy and more opaque, perfect for hearty gravies and stews.
- Wine or broth slurry: Replace the water with wine, stock, or even fruit juice for extra flavor. Ensure the liquid is cold to prevent lumps.
Storage and Reheating
Slurry is best used immediately, but you can store an unused slurry in an airtight container in the refrigerator for up to 2 days. Give it a good whisk before using, as the starch will settle. Do not freeze a slurry—thawing will cause the starch to break down and lose thickening power. Leftover thickened dishes (like gravy or sauce) can be refrigerated for 3–4 days. Reheat gently on the stovetop over low heat, stirring often; if the sauce has thinned, whisk in a fresh slurry (1 tsp starch + 2 tsp cold water) and simmer until thickened again.
Frequently Asked Questions
Can I use hot liquid to make a slurry? No—hot liquid will cause the starch to gelatinize immediately and form lumps. Always mix the starch with a cold liquid first, then add it to the hot mixture.
Why did my slurry turn out lumpy? Lumps usually form because the starch was not fully dissolved in the cold liquid, or because you added the slurry to liquid that was not hot enough. Whisk the slurry thoroughly, and make sure your hot liquid is simmering before adding.
Why is my sauce not thickening? Possible reasons: the liquid was not simmering, you did not use enough starch, or you added an acidic ingredient that broke down the starch. Try increasing the starch amount slightly and ensure a gentle simmer.
Can I use a slurry to thicken cold liquids? No—starch needs heat to gelatinize. For cold preparations like salad dressings, use a gum like xanthan or a pre-cooked starch like instant tapioca.
What is the difference between a slurry and a roux? A roux is made by cooking flour in fat (butter or oil) before adding liquid, which adds flavor and color. A slurry is a quick, raw mixture of starch and cold liquid, added at the end of cooking. Slurries are faster but do not add flavor.
Can I double the recipe? Yes, simply scale up the starch and cold liquid in the same ratio (1:2 for cornstarch). For larger batches, use a bowl large enough to whisk thoroughly.
Related
- How to Simmer in a Large Pot: Tips & Timing
- Simmering Beef Soup: A Hearty One-Pot Recipe
- Simmering Beef Stew Recipe: Rich & Hearty
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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