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Thicken Any Slow-Cooker Dish: 6 Quick & Easy Fixes

Your slow cooker dish turned out too thin? We’re serving up quick and foolproof fixes that’ll get you back on track.

The slow cooker—a bonafide kitchen helper that turns raw ingredients into mouthwatering meals while you go about your day.

But what happens when you open the lid, eager for a hearty stew or savory sauce, only to find it’s more soup than substance? Don’t despair; your slow-cooked dish is but a few tweaks away from the ideal thickness.

Whether you’re a slow-cooker beginner or a Crock-Pot power user, we’re written this guide to give you the foolproof methods for thickening any sauce soup, or stew to just the right consistency. Let’s dive in!

How to Thicken a Sauce, Soup, or Stew in the Slow Cooker

The fixes:

  1. Simmer off the moisture
  2. Make a roux
  3. Make a cornstarch slurry
  4. Add puréed potatoes
  5. Add shredded cheese
  6. Blend part of the dish

Fix #1: Cook with the lid cracked open.

The lid of your slow cooker is there to keep the moisture in, so that your food stays moist and cooks evenly. Normally, you’ll want to keep the lid in place while cooking.

If your slow-cooker dish is too watery, you can thicken it by removing the lid and allowing some of the moisture to evaporate. Be cautious with this approach: leave the lid off only long enough to thicken the sauce. Any longer, and you risk drying out your dish.

Slow cookers are designed to be used with the lid in place—for reasons of safety and efficiency—and you may need a workaround to keep the lid open. Most of the time, a wooden spoon can do the trick. Place it between the pot and the lid to allow moisture to escape. Just make sure the spoon is secure and won’t slip.

Fix #2: Make a roux and stir it into your slow-cooker dish.

A roux (pronounced “roo,” like in “rooster”) is the staple thickener in both French and Cajun/Creole cuisines. It does wonders for thickening gumbo and beef stew. It’s made by cooking equal parts unsalted butter and all-purpose flour together until they form a smooth, uniform paste.

To make a roux, weigh equal amounts of flour and butter. Place the butter in a saucepan and melt it over medium-low heat. Once the butter is fully melted, gradually whisk in the flour. Continue to cook the mixture, stirring continuously, until it turns a pale white color. This change in color indicates that the raw-flour taste has been cooked off.

Finally, stir the prepared roux into your dish in the slow cooker. Close the lid and allow it to cook for at least a few more minutes to let the flavors meld together. You’ll need to mix in the roux thoroughly to distribute it evenly. To protect your pot’s non-stick coating, use a silicone spatula or spoon, which will prevent scratches.

Note: You can continue to cook the roux after it has turned white. The longer you cook it, the darker it will become, changing from a white roux to blond one, and then to brown. The darker the roux, the richer and nuttier the flavor will be.

However, the richer flavor comes at the expense of its thickening power. If your primary goal is to thicken a sauce or soup—and you’re here reading this, so it probably is—a white roux is the best choice.

Fix #3: Make a cornstarch slurry and work it in.

A cornstarch slurry is ideal for thickening your slow-cooker dish without the buttery decadence of a roux. Cornstarch is a gluten-free alternative that works like a charm, especially in Asian dishes or gravies where a clear, glossy finish is desired.

To make a cornstarch slurry, you’ll need cornstarch and cold water. The ratio is 1 part cornstarch to 2 parts cold water. So, if you’re using a tablespoon of cornstarch, you’ll want to mix it with two tablespoons of cold water. Stir it up in a small bowl until it forms a smooth, lump-free paste. This is your slurry.

Take a moment to consider the temperature of your dish. Cornstarch activates at high heat, so make sure your slow-cooker contents are bubbling away. If they’re not, crank up the heat setting until they are.

Once you’re at the right temp, go ahead and pour in the slurry while stirring the dish. This ensures even distribution, so you won’t end up with gloopy pockets of cornstarch. Give it a good mix, reduce the heat, then close the lid. Let it cook for an additional 10 to 15 minutes.

Fix #4: Add potato purée and let the starch do the work for you.

Adding mashed potatoes to your slow-cooker sauce, soup, or stew will make it lumpy. But if you use puréed potatoes—either store-bought instant flakes or potatoes you’ve blended yourself—you can thicken it up beautifully, without any lumps. This technique shines in robust vegetable stews, already high in starches.

Potato purée works particularly well in hearty stews and meat-based sauces. The key to thickening your slow-cooker dish with potato purée lies in moderation. Add too little, and the dish won’t thicken. Add too much, and you risk overpowering the other flavors, inadvertently turning your dish into a potato stew.

If in doubt, start with a tablespoon and adjust from there. Remember, you can always add more purée later to thicken your dish, but you can’t take it away if you add too much.

Fix #5. Use shredded cheese as a thickening agent.

Cheese isn’t just for melting on top of sandwiches or sprinkling over pasta. When chosen carefully, it can also serve as an effective thickener for your slow-cooker sauce, soup, or stew.

Creamy, melt-in-your-mouth cheeses like cheddar, Gruyère, or fontina work particularly well. I’ve also had success with hard Italian cheeses, like Grana Padano, Parmigiano-Reggiano, and Pecorino Romano. Just be mindful of the salt content in the cheese—adding too much can cause your dish to turn out a little too salty.

For best results, add grated or finely chopped cheese during the last 15 to 30 minutes of cooking. This allows enough time for it to melt and fully incorporate into the dish. Keep in mind that using cheese as a thickener will not only make your cooking liquid thicker but also impart a cheesy, gooey texture and flavor.

While this technique works well for comfort foods, like macaroni and cheese or a hearty potato soup, it may clash with lighter, more delicate dishes such as a spring vegetable stew or seafood bisque.

Fix #6. Blend part of the dish and pour it back into the slow cooker.

This technique of using blended vegetables as a thickener is not suitable for meat dishes, as blended meat is more or less unpalatable. But it’s an excellent option for vegan or vegetarian dishes, especially hearty vegetable stews and soups.

Here’s how it works: Simply remove about a third of the dish—both liquid and vegetable chunks—and blend until it forms a creamy consistency. Before blending, allow the portion you’ve removed to cool slightly to avoid potential splatter and burns. Then, reintroduce this mixture back into the slow cooker. Continue cooking for at least an additional 5 minutes to allow the flavors to meld together.

What We’ve Just Covered

Now, you have the tips and tricks up your sleeve to thicken any slow-cooker dish, no matter how watery it turned out.

Whether by simmering out the liquid, making a roux, making a cornstarch slurry, adding potato purée, shredding cheese, or blending some of the cooking liquid, these techniques offer a quick and simple fix for every recipe. The next time you find yourself staring into a slow cooker filled with a too-thin sauce, soup, or stew, remember: the desired thickness is just a spoonful—or a sprinkle—away.

Know your author

Written by

Dim is a food writer, cookbook author, and the editor of Home Cook World. His first book, Cooking Methods & Techniques, was published in 2022. He is a certified food handler with Level 1 and Level 2 Certificates in Food Hygiene and Safety for Catering, and a trained cook with a Level 3 Professional Chef Diploma.