1. Corn Starch
Why it works: Corn starch is a go-to when thickening sauce for good reason: It’s widely available, inexpensive, flavorless and highly effective at thickening, even in small amounts. It also makes a translucent mixture when heated (which is why it’s sometimes preferred over flour). Corn starch is a type of carbohydrate that comes from corn kernels. When it’s mixed with liquid and heated, it becomes gelatinous and thick.
How to use it: To thicken sauce with corn starch, use about 1 tablespoon per cup of sauce. You’ll first want to create a slurry by whisking the corn starch into an equal amount of cold water—this will prevent clumping when you add it to the hot sauce. While whisking the sauce over medium heat, slowly pour in the slurry and continue to whisk while bringing the sauce to a boil for 1 minute. This is crucial; the corn starch is activated by heat and won’t thicken properly if you don’t cook it long enough.
When to use it: Corn starch is a great option for thickening clear sauces (like stock- or soy-based sauces). It breaks down in the presence of acid, so skip it for anything acidic. It’s also a good thickener for custards, puddings and baking recipes.
Why it works: Flour is a classic sauce thickener, whether you’re making gravy, béchamel, gumbo or stew. You probably already have it in your pantry. When added to a liquid, the starches in the flour expand and add body to the sauce.
How to use it: To thicken sauce with flour, you’ll want to cook off its raw taste first. This is done by making a roux, an equal mixture of melted butter and flour. Melt the butter in a skillet over medium heat, then whisk in the flour and cook until it’s golden brown and smells nutty. The roux can then be added to your sauce and whisked to combine.
When to use it: Use flour to thicken gravy, soup, stew and dairy-based sauces. Keep in mind that it will make your sauce cloudier than corn starch will (and it won’t thicken quite as much).
3. Egg Yolk
Why it works: Egg yolks contain lots of protein, which will thicken a sauce when heated. Depending on how thick you want to make your sauce, you can play around with how many yolks to add (but start with one or two).
How to use it: First, separate the egg yolks from the whites into a bowl. To prevent the yolks from scrambling into the sauce (gross), you’ll want to temper it by whisking a small amount of the hot sauce into the egg yolk, then adding that mixture back into the rest of the sauce.
When to use it: Egg yolks are especially tasty in pasta sauces because they add richness without being gloppy. They can also thicken salad dressings, cream sauces and custards.
Why it works: While adding a knob of butter to a sauce won’t thicken it dramatically, it can be just the thing to add extra richness and a glossy texture.
How to use it: At the end of cooking, swirl a few tablespoons of cold butter into the sauce off the heat. (If it gets too hot, the sauce will break and end up greasy instead of glossy.)
When to use it: Butter is an excellent addition to pasta sauces and pan sauces that don’t need to be too thick but could use a little oomph.
5. Reducing the Liquid
Why it works: Reducing a sauce evaporates the water content, so your sauce gets thick without adding any extra ingredients. It also concentrates the flavor, which can be desirable in some dishes.
How to do it: Simply cook your sauce over medium heat until the amount looks reduced and the texture is as thick as you want it. (You can test it by coating the back of a spoon.) You’ll also want to be sure to season the sauce at the end, otherwise it can taste too salty if it reduces too much.
When to do it: Reducing will make your sauce thick but not too thick or gloppy, so it’s a good method for pan sauces and pasta sauces. Skip it for anything with soy sauce or lots of salt.
Why it works: Arrowroot is almost identical to corn starch, but it’s derived from the arrowroot tuber, a tropical plant. It thickens just like corn starch too, but it’s even smoother and clearer and thickens at a lower temperature. It also doesn’t break down when mixed with acids and can be frozen. It’s also gluten-free.
How to use it: You can thicken sauce with arrowroot just like you would with corn starch. Use about 1 tablespoon per cup of sauce. First, create a slurry by whisking the arrowroot into an equal amount of cold water. While whisking the sauce over medium heat, slowly pour in the slurry and continue to whisk while bringing the sauce to a boil for 1 minute.
When to use it: Use arrowroot in place of corn starch or in sauces that contain acidic ingredients (like lemon juice or vinegar). Skip it in dairy-based sauces, because it can get slimy.
7. Beurre Manié
Why it works: Beurre manié is French for “kneaded butter,” and it’s a mixture of equal parts soft butter and flour. It’s similar to a roux but eliminates the possibility of lumps by releasing the flour evenly and slowly into the sauce.
How to use it: To make a beurre manié, knead together equal amounts of butter and flour in a small bowl until it’s the texture of playdough. Then it can be slipped into your sauce and whisked until combined. You’ll want to continue to cook the sauce and taste as you go to ensure the raw flour taste has been cooked out.
When to use it: Use a beurre manié to finish sauces, soups and stews and to thicken sauces that you want to be lump-free and glossy.