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How to Thicken Onion Soup: 10 Easy Ways

Thickening onion soup is a quick and easy way to give it more body. While many people prefer to use flour or cornstarch to thicken the soup, you can also opt for a healthy alternative like chickpeas, beans, or lentils.

See Also: what sandwich goes with french onion soup?

How to Thicken Onion Soup

Onion soup is something that everyone loves, but what if you want to turn it into something more?

See Also: What Salad Goes with French Onion Soup? 10 Best Salads

You know what I mean. You want your bowl of soup to be rich and creamy, but you’re also looking to make it as healthy as possible.

That’s where thickening up onion soup comes in.

Thickening the soup not only increases the texture and flavor of the soup, but it also makes it a bit more filling.

Today, I’m going to show you how to make an onion soup thicker!

So without further ado, let’s get started!

See Also: 50 Best Soups with Turnips

How to Thicken Onion Soup: 10 Easy Ways

How to Thicken Onion Soup

You can thicken onion soup by using bread crumbs, cooked rice, or flour. Cook the soup until it begins to thicken and then add the bread crumbs or rice to the soup. Stir until the soup is smooth and creamy.

Here are 10 other ways to thicken onion soup:

1. Oatmeal


A great way to thicken an onion soup without the need for any special ingredients is with oatmeal.

This is a very easy way to add a thick, creamy consistency to your soup without the need to add any other ingredients.

If you’ve never added oats to a recipe before, don’t be intimidated. Simply add about a cup of oats to a pot of simmering water over medium heat and let them cook until they’re soft and have absorbed all the liquid.

Remove the pot from the heat and strain the oats into a measuring cup. You’ll be left with a perfectly thickened liquid that can be used in your soup!

2. Flour and Water


If you’re looking for a simple way to thicken onion soup without having to add more ingredients, a mixture of flour and water is just the ticket!

A roux is one option that I’ve heard of, but it takes more time and effort than this method.

Mix equal parts flour and water together and cook over medium heat while stirring constantly. You can do this by heating up a separate pan and melting the butter in it.

Once your butter has melted, pour it in the bowl with the flour and water, and stir until it turns into a thick paste.

This can be used on top of or in place of a roux.

3. Arrowroot

Arrowroot powder

If your soup still isn’t thickening up, you might need to add more vegetables or even a roux.

But if you’re not opposed to adding a thickener that requires a little more effort, arrowroot starch is a common option.

Related: 19 Arrowroot Recipes to Satisfy Your Appetite

Arrowroot is often used to thicken sauces with its natural properties, which include being naturally gluten-free and starchy.

It doesn’t contain any flour, so it won’t leave a powdery taste like flour-based thickeners can do. It also doesn’t have any of the sugar content flour does either.

To make arrowroot, simply add 1 teaspoon of the powder to a cup of cold water and whisk until the starch becomes visible.

You can use this starch in the same way you would a roux, by whisking it into your sauce.

4. Cornstarch


If you prefer not to use a roux, there’s a more straightforward way to thicken your onion soup that doesn’t require much effort or a special ingredient.

Cornstarch is commonly used in Chinese cooking. It acts as a thickening agent when mixed with water.

Simply add a small amount of cornstarch to a pot of boiling water. Stir constantly while adding more cornstarch until it reaches a desired thickness.

A few spoonfuls will do the trick. Once you’ve added enough, turn off the heat and let the mixture sit for 5 minutes before serving.

5. Tapioca Flour

Tapioca flour

For all those onion soup lovers out there, I have an alternative to a roux or a flour-based thickener!

Tapioca flour is actually a starch extracted from cassava root. It’s used in French cooking as well as in Asian dishes.

Unlike a flour-based roux, tapioca flour does not contain gluten. This means you’ll never get that bread-like consistency.

Tapioca flour is commonly added directly to the soup. Since it’s not a liquid, it will not break down when adding it to the soup. You’ll just need to stir it into the broth.

6. Egg Yolks

egg yolk

If you’re looking to thicken an onion soup, you can take advantage of the richness of the egg yolks.

Egg yolks work as a great thickener for any kind of soup, but they are particularly useful for onion soup.

In a small bowl, whisk together 2 egg yolks and a pinch of salt until combined.

Add a bit of water to the bowl and mix with a spatula until smooth and creamy.

Pour the mixture into the soup while it’s hot and serve immediately.

This method works best when using mild or sweet onions, so choose wisely. If you go with the traditional French recipe, you’ll want to use shallots.

7. Reduce the Soup

Reduce the Soup

One of the easiest ways to thicken your soup is by reducing it. This is the process of boiling off excess liquid and allowing the soup to boil down naturally, which will help thicken it up.

If you’re simmering your soup, do not let it boil too long. You should reduce the heat to a low simmer after about 30 minutes, and continue until it’s done.

8. Add Butter


Thickening your soup with butter is one of the simplest methods.

This method requires less effort than other techniques and doesn’t require you to make a roux.

Just add a spoonful of butter to your soup. Once it has melted, add more butter in small increments.

If you want it thicker, add more butter. If you prefer it thinner, add less. It’s up to you!

9. Add Mashed Beans

Mashed Beans

This is a quick method to thicken onion soup that doesn’t require any additional ingredients or preparation.

If your soup has already simmered for several hours, it’s time to take the beans in.

Mash up some of your beans while they’re still hot and pour them into your broth. Stir until the beans have completely incorporated.

This method will leave your soup thicker than the others, but it’s a quick fix that works well in any circumstance.

10. Add Cheese

shredded cheese

Cheese is another classic way to thicken soups. If your soup is really thin, add a cup or two of shredded cheese to your soup.

This step should be done just prior to serving. You want to make sure your soup has the time it needs to soften the cheese up a bit.

The cheese should be crumbled into the soup rather than stirred in to help prevent chunks of cheese from forming in the sauce.

How to Thicken Onion Soup: 10 Easy Ways

If you’re looking to thicken onion soup, you’ll want to add flour or cornstarch to your soup.
You can also use a roux (a mixture of butter and flour) to thicken the soup.
If you prefer a creamy texture, you can also add milk or cream.
Prep Time3 minutes
Active Time3 minutes
Total Time6 minutes
Course: Soup
Cuisine: French
Keyword: How to Thicken Onion Soup
Cost: 1


  • Oatmeal
  • Flour and Water
  • Arrowroot
  • Cornstarch
  • Tapioca
  • Egg Yolks
  • Reduce the Soup
  • Add Butter
  • Add Mashed Beans
  • Add Cheese