All-purpose flour is an easy substitute for cornstarch when you need to thicken a savory sauce: use about twice as much flour, mixed with cold water, as the cornstarch called for. This simple flour-thickened broth sauce shows the method, while the notes below explain how other pantry starches behave and how to choose the right swap for your dish.
Ingredients
- 2 cups (480 ml) low-sodium chicken or vegetable broth
- 1/4 cup (30 g) all-purpose flour
- 1/2 cup (120 ml) cold water
- 1 tablespoon (14 g) unsalted butter
- 1/4 teaspoon (0.75 g) garlic powder
- 1/8 teaspoon (0.3 g) ground black pepper
- 1/4 teaspoon (1.5 g) fine salt, plus more to taste
- 1 teaspoon (5 ml) soy sauce, optional, for a deeper savory flavor
Instructions
- Make the flour slurry. Put the flour in a small bowl and gradually whisk in the cold water until no dry pockets or lumps remain. Set it beside the stove. Stir it again just before using, since flour can settle to the bottom while it stands.
- Warm the broth. Add the broth, butter, garlic powder, and black pepper to a medium saucepan. Set over medium heat and stir until the butter melts and the broth is steaming, about 3 minutes. It does not need to boil.
- Add the slurry gradually. Whisk the flour-and-water mixture once more, then pour it into the hot broth in a steady stream while whisking continuously. Keep whisking for about 1 minute so the flour disperses evenly instead of forming clumps.
- Simmer until thickened. Lower the heat to medium-low and cook at a gentle simmer for 6 minutes, stirring often and scraping the bottom and corners of the pan. The sauce should coat the back of a spoon. If it is still thinner than you want, simmer for another minute or two; if it becomes too thick, whisk in warm broth or water a tablespoon at a time.
- Season and serve. Stir in the optional soy sauce and salt, taste, and adjust the seasoning. Serve hot. The sauce will thicken a little more as it stands, so take it off the heat when it is just slightly looser than your desired final consistency.
Tips
- Use the right conversion. For a typical sauce, start with 2 tablespoons (about 15 g) all-purpose flour for every 1 tablespoon (about 8 g) of cornstarch in the original recipe. Flour thickening is less potent by volume, so swapping equal spoonfuls usually gives a thinner result. If you are adjusting a large pot, add only part of the flour mixture first, simmer, and assess before adding more.
- Always mix flour with cool liquid first. Whisking dry flour directly into hot broth is a common cause of stubborn lumps. Cold water makes a smooth slurry; alternatively, whisk flour into softened butter to make a paste. If small lumps remain, pass the finished sauce through a fine-mesh strainer.
- Give flour time to cook. A flour-thickened sauce needs several minutes at a gentle simmer to lose its raw, pasty taste. Keep it below a hard boil and stir frequently, especially if the sauce contains dairy or a sugary ingredient that can catch on the pan.
- Expect a different finish. Cornstarch usually makes a glossy, somewhat translucent sauce, while wheat flour makes it more opaque and soft-looking. Flour also contains gluten, so it is not suitable for someone avoiding gluten; use a gluten-free starch or a labeled gluten-free flour blend instead.
Serving Suggestions
This flexible savory sauce works over mashed potatoes, rice, roasted vegetables, biscuits, or sliced cooked meat. Spoon it over the food shortly before serving so the coating stays smooth. For a simple weeknight meal, pair it with roast chicken or baked tofu and a green vegetable; the broth and pepper make a mild base that does not compete with strongly seasoned sides.
Use the recipe as written for a lightly seasoned sauce, or build more flavor before thickening. For example, brown sliced mushrooms in the butter, then add the broth and continue with the slurry. You can also whisk in pan drippings, but taste before adding salt because drippings and prepared broth can both be salty. If the sauce is intended for noodles or a casserole, keep it a little thinner than a table sauce: it will continue to absorb moisture as it sits with the other ingredients.
Variations
Use a roux instead of a slurry. Melt the butter over medium heat, whisk in the flour, and cook for 1 to 2 minutes, stirring constantly, before gradually whisking in the broth. This traditional method makes a smooth, rounded sauce and removes the need for the separate cold-water slurry. Cook the roux only until pale blond for a neutral flavor; a darker roux tastes nuttier but thickens less effectively, so it may need extra flour.
Choose another starch. For a gluten-free option, arrowroot can generally replace cornstarch in equal amounts and gives a clear, glossy finish, but it can become stringy if boiled hard and does not hold up as well to prolonged heating. Tapioca starch also gives shine and can feel slightly stretchy; start with the same amount as cornstarch and avoid extended boiling. Potato starch thickens quickly and can make a silky sauce, but add it near the end and do not simmer it for a long time. For these alternatives, make a cold-water slurry and follow the package directions if they give a different ratio.
Make it creamy or herb-forward. Replace up to 1/2 cup (120 ml) of the broth with milk or unsweetened cream, then keep the sauce at a gentle simmer rather than letting it boil. For a fresh finish, stir in 1 tablespoon (about 4 g) chopped parsley or chives after turning off the heat. A small squeeze of lemon can brighten the flavor, though add it gradually and taste so the sauce does not become too sharp.
Adjust the consistency for the job. A thinner sauce for drizzling needs less thickener; a gravy meant to cling to a spoon needs more. Rather than putting extra dry flour straight into a finished sauce, whisk 1 tablespoon (8 g) flour with 2 tablespoons (30 ml) cold water in a small bowl, add a little of that slurry, and simmer for several minutes before deciding whether to add more. This gradual approach is easier to control than trying to correct an overly thick sauce afterward.
Storage and Reheating
Cool the sauce promptly and refrigerate it within 2 hours in a covered container. It keeps for 3 to 4 days in the refrigerator. Flour-thickened sauce can form a skin or become quite firm when cold; that is normal, and a thorough stir while reheating usually brings it back together. Do not leave the sauce at room temperature for extended storage.
Reheat gently in a saucepan over low to medium-low heat, stirring frequently. Add broth or water a tablespoon at a time if it has thickened too much, and warm only until steaming and smooth. A microwave also works: heat in short 20- to 30-second intervals, stirring between each one. For food-safety purposes, USDA FSIS recommends reheating leftovers to 165°F (74°C); check the temperature with a food thermometer if serving as reheated leftovers. Avoid repeated cooling and reheating, which can make the texture less even.
For longer storage, freeze the sauce in a freezer-safe container for up to 2 months for best quality, leaving a little room for expansion. Thaw it in the refrigerator, then reheat gently while whisking. Some separation can occur after freezing, particularly if the sauce includes dairy; whisking in a splash of broth often helps, though the texture may not be quite as glossy as when freshly made.
Frequently Asked Questions
How much flour should I use instead of cornstarch?
Use about 2 tablespoons (15 g) of all-purpose flour for each 1 tablespoon (8 g) of cornstarch. This is a useful starting point for sauces and gravies, but the exact amount depends on how much liquid the recipe contains and how thick you want the result. Add it gradually and allow time for the sauce to simmer before judging the final texture.
Can I add flour directly to hot sauce?
It is better not to. Dry flour can form lumps as soon as it hits hot liquid, and those lumps are difficult to whisk smooth. Mix flour with cold water to make a slurry, or make a butter-and-flour roux before adding the liquid. Either method disperses the flour more evenly.
Will flour make sauce taste different from cornstarch?
Yes, slightly. Flour gives sauce a more opaque, soft finish and can taste starchy if it is not simmered long enough. Cornstarch creates a clearer, glossier coating and thickens quickly. In a strongly flavored sauce, the difference may be subtle, but flour is less suitable when a bright, transparent finish is important.
What is the best gluten-free substitute for cornstarch?
Arrowroot, tapioca starch, and potato starch are common choices. Arrowroot is a good option for a clear finish, while potato starch thickens quickly and tapioca can give a glossy, slightly elastic texture. Their performance varies with acidity, heat, and cooking time, so add them as a slurry and avoid prolonged boiling unless the product instructions specifically allow it.
Can I use plain flour to thicken a sauce that is already finished?
Yes, but do not sprinkle it straight into the pan. Whisk flour with cold water until smooth, then whisk a small amount into the sauce and simmer for at least 5 minutes to cook out the raw flavor. If the sauce is already seasoned, make a small test portion first so you can judge how the flour affects both texture and taste.
Why did my flour-thickened sauce turn lumpy or too thick?
Lumps usually mean the flour was not dispersed before it met the hot liquid, or the slurry was not whisked as it went in. Too much flour, too much reduction, or extra simmering can make the sauce overly thick. Whisk in warm broth or water a little at a time; if there are persistent lumps, strain the sauce before serving.
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