It’s that time of year again. Where kitchens are filled with the aromas of soups, stews, gravies and at my house, stir-frys. As the colder weather creeps in and the holiday season approaches there will be many of us making roux and slurries to thicken our breakfast tomato gravy and chunky chowders. But how do we know when to use a roux over a slurry or vice versa?

First you’ll need to know how to make each and when to use them!

How to Make a Roux

A roux is equal parts flour and fat. You can use oil, but traditionally the fat used is butter which gives it a nice nutty flavor to add to your dish. A roux is used for thickening gravy, sauces, soups and stews. A roux also is cooked to different colors for different dishes. You have your white roux for mac and cheese, brown roux for soups and sauces and then dark brown roux for creole dishes like gumbo!

If you’re making a white roux, you’ll only need to let it simmer and stir frequently for about 5 minutes. Then you would typically add milk and continue to stir while it thickens over heat.

For a brown roux, I like to make the roux and then add about 1 to 1.5 cups of the broth I’m using as the base of the soup.

For a dark brown roux, you’ll want to simmer it on low and stir frequently for up to 45 minutes to achieve that deep golden brown color. This way you’ve really cooked out the flavor of the flour but the butter is browned and nutty. This method is what makes an authentic gumbo super delicious.

Fun fact, roux is actually translated to “browned butter”!

How to Make a Slurry

A slurry is 1:2 ratio of starch and liquid, typically water or milk. Slurries are used to help thicken soups, sauces and stews.

Though starch is the more common ingredient, you can use flour, however using starch will keep the slurry more translucent. Using flour in a slurry also takes a little longer for your food to thicken because flour takes a little longer to activate.

To make a slurry, combine your starch and liquid into a small bowl and whisk until the starch is dissolved. I use slurries a lot for my stirfrys and you can also mix the starch right into your stir fry sauce! Be careful not to overcook your slurry. This can cause it to thin out. The best way to thicken your food with a slurry is to make sure your pan is hot and add the slurry then remove your pan from the heat.

With a stir fry, I make sure my veggies/meat are cooked all the way then add the slurry and remove it from the heat then continue stirring until it’s thickened.

Same goes for soups, I’ll add a ladle of my soup base to a small bowl and add in about 1-2tbsp of cornstarch, mix until it’s dissolved and make sure my soup is off the heat before adding my slurry back in.

How Are They Different

So a roux and a slurry are both used to thicken sauces, soups and stews. Then how are they different?

The first thing we know about flour vs cornstarch is that cornstarch is gluten free. Although you could use a gluten free flour for your roux.

A roux is more time-consuming where a slurry is almost instant. A roux can take anywhere from 5-45 minutes to prepare where a slurry is mixed until dissolved and almost instantly thickens your food.

A slurry is a little more difficult to perfect than a roux. You constantly keep your roux heated where your slurry will be a cold mixture from the start. Your roux is 1:1 flour and butter and you stir it frequently over low heat, a slurry is 1:2 of starch and liquid that thickens through the cooling process.

Remember, if you overcook your slurry it could thin out and you’d have to start all over. This is why you should remove your pan from the heat once your slurry is poured in. Overcooking could also produce a chalky flavor which might ruin your whole meal altogether.

When to Use a Roux

Remember, you’ll want to make a roux for gravy, sauces, soups and stews. We are a gluten free household and I always make a roux with gluten free flour and butter. I don’t make a roux very often, except for when I surprise my girlfriend with biscuits and skillet potatoes. One recipe she taught me was tomato gravy and my life was forever changed. But the perfect base to a tomato gravy is a nutty roux.

I cook my gravy roux to a light brown color and then toss in a can of tomatoes or chopped fresh roma tomatoes.

Other recipes I use a roux in are thicker soups. This time of year I love whipping up new soups each week for lunches. In thicker soup recipes, like chowders or even potato soup, it takes it up a notch to add a roux. With this type of roux I usually add milk to coconut milk to the roux since that will be my base for the soup.

One recipe I don’t make very much, but I have before on occasion is gumbo. With this you have to have a roux. No questions asked. And if you have the time to prep ahead, it’s worth making a dark brown roux. It does take about 45 minutes, but it’s totally worth it.

When to Use a Slurry

And then for your slurry, you’ll want to make this for sauces soups and stews. I like to use a slurry for my soups if I didn’t thicken it enough from the get go. Say it’s getting close to serving time and the consistency is a little to loose for your taste. Grab a small bowl, scoop out a ladle of your soup base (try to avoid collecting any vegetables or meat) and add 1-2tbsp of starch to the bowl. Whisk with a fork until the starch is dissolved and add this back to your soup and stir in until mixed. Turn off the heat and give it a few minutes and you’ll notice your soup start to thicken. And just repeat that process until it’s your preferred consistency!

But what I mostly use slurries for are my stirfrys. I make a tofu dish once a week and tofu is nothing without a sauce. My sauce usually consists of coconut aminos, sesame oil, ponzu sauce, fish sauce, lemon juice etc. In this case, I just mix my starch straight into the sauce without adding any additional liquid. Once I’ve fried or baked my tofu, I toss the sauce into a hot pan and remove it from the heat stirring consistently. Within no time the sauce will thicken up and coat the tofu perfectly!

Which do you prefer to use, a roux or a slurry? Or do you alternate between both like me? Let me know in the comments below!

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Remember to be brave in trying new things and always cook with a dash of love!

Until next time,

Haley | Creator of Haley’s Kitchen

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  1. I love your Slurry vs Roux, you have explained the differences well. I have to admit, I’ve never heard of the term slurry as a thickening, but now I know what it is. I prefer to use better in my roux. It’s not the same using oil, however there are plenty of different flavours on the supermarket shelves these days and would provide a range of flavours. Thank you for sharing.

    1. Thank you so much! I definitely prefer butter over oil in a roux, too.

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