How To Thicken Pesto Sauce ⋆ The 6 Most Effective Options ⋆

The best way to enjoy a freshly made pesto sauce is with your favorite kind of pasta. I am sure you agree with me. But what if your pesto turns out thin and runny? Do not worry! Thankfully, you can still save it. But how do you improve the consistency? Here are the best ways to do so effectively.

So, how do you thicken a pesto sauce? The best way to thicken a pesto sauce is to add a few ingredients that will reduce the liquid content, increasing concentration. Some of these ingredients include – pine nuts, basil leaves, cheese, breadcrumbs, pasta water, or cornstarch.

While making pesto from scratch is generally very quick and easy, sometimes it turns out thin and just doesn’t cling to foods in the way we have come to expect.

For a good consistency for pesto, use your judgment for the addition of the above ingredients. 

You may need more or less, depending on the pesto you are working with.

When it comes to your options, personal preferences and the availability of ingredients can help you decide on the method you choose.

You might like to use one or a combination of these methods.

Nevertheless, are you ready to dive deeper and see how these options can work? 

We’ll soon get into it.

But first, why is your pesto sauce so thin to begin with? 

Why Is My Pesto Sauce Thin?

Pesto sauce can be thin or runny because you added too few pine nuts or you drizzled too much olive oil. However, it could also be that you added too much pasta water, too. 

Ultimately, you are trying to create a fine balance. 

Pesto is an emulsion where the two liquids – water and oil do not mix with each other but retain their individual characteristics when processed together. 

The water phase comes from basil leaves, garlic, and the oil phase is the olive oil used. 

The organic compounds in basil and garlic help to stabilize this emulsion.

And lastly, you have the pine nuts, which add some consistency too. 

How Thick Should A Pesto Sauce Be?

A perfect pesto sauce is thick and has a slightly coarse texture. It has a pasty consistency and is not uniformly smooth. The word pesto literally means ‘paste’ and originates from its traditional method of preparation where the ingredients were ‘crushed’ or ‘pounded’ using a mortar and pestle.

But how do you know your pesto is thick enough? 

The consistency can range from anywhere between a puree and a spread, depending on the ingredients used for making the pesto. The sauce falls like a ‘glob’ from the spoon if it is thick. 

If the sauce is a puree, it leaves a residue on the back of your spoon. 

The addition of olive oil into the pulverized ingredients is critical here. 

The addition of the oil should be very slow if you need a smoother texture. 

If oil is poured speedily, the crushed ingredients do not have sufficient time to puree and are not homogenized, and the sauce tends to separate.

One thing to note here is that desired consistency is also based on personal preferences and how you intend to use the pesto.  

What Can You Use To Thicken Pesto Sauce?

If your pesto sauce is thin, you can easily thicken it by adding one of these ingredients – pine nuts, basil leaves, cheese, breadcrumbs, pasta water, or cornstarch.

Remember, you must add existing ingredients that are integral to the recipe. 

This will help bind the excess moisture in the sauce but also retain the right flavors.

One thing is for sure; do not add any liquid or more olive oil to the pesto.

How To Thicken Pesto Sauce – Step by Step

The below options will all enable you to thicken your pesto depending on the ingredients you have to hand in, or the time you have available. 

Nonetheless, the easiest way is to just add more of the base ingredients.

Usually, it is best to use a combination of these techniques to attain a thick and tasty sauce.

Thickening With More Pine Nuts 

This is the simplest method to thicken your pesto sauce.

This method will give a body to your sauce and thicken it. 

Here’s what you need to do:

  1. Add the extra pine nuts to the mixture,
  2. Pulverize it in the food processor till the contents are well blended,
  3. Check the consistency of the sauce you are after.

If you run out of pine nuts, you may want to consider swapping them out with walnuts, almonds, sunflower seeds, and even pumpkin seeds. 

But do consider that each of these will introduce a new flavor to your pesto.

Equally, do remember to slightly roast the nuts or seeds for a better flavor before processing them in a food processor. 

Also, ensure that you are using fresh nuts and there’s no rancid smell in them. 

This can easily ruin the taste of your pesto sauce.

Thickening With More Basil Leaves 

You can use extra basil leaves to quickly thicken up your pesto.  

Here’s how you can do it:

  1. Add the extra basil leaves to the thin sauce,
  2. Pulse it in the food processor till the contents are well combined, 
  3. Check for the desired consistency.

If you need to add a lot of basil, then this might alter the taste and flavor of the pesto. 

Basil, when in large amounts, can result in a bitter pesto, and consequently, you will need to add more of the other ingredients to balance out the taste.

If you have no basil leaves left, you can use spinach instead. 

Just add some chopped spinach to the pesto and pulse in the food processor. 

This will thicken your sauce without changing the flavor.

Some people like to add other leafy greens like kale, arugula, or parsley to the pesto for variety and to improve the nutritive value of the sauce.

But again, do consider some subtle flavor changes if you do go this route!

Thickening With More Cheese 

Cheese has a thickening effect on the sauce and will make it creamier as well. This is how you can do it.

  1. Grate the cheese finely and then add it to the sauce,
  2. Pulse it in the food processor till the contents blend well,
  3. Check for the desired consistency.

It is recommended you use hard, salty cheese like Parmesan for that lovely texture. 

So, avoid using soft cheeses like brie or mozzarella! 

Thickening With Breadcrumbs

You can throw in some breadcrumbs to your runny pesto.  

These are often readily available in your pantry, so they are a great choice. 

Just follow these steps:

  1. Add the breadcrumbs to the sauce,
  2. Pulse it in the food processor until combined,
  3. Check for the desired thickening.

Also, make sure that you use unseasoned breadcrumbs to not alter the pesto flavor.

You can even use leftover bread pieces/ crust or croutons if you do not have breadcrumbs on hand.

Thickening With Boiled Pasta Water

Pasta water comes in handy when you are ready to mix the pesto sauce with the pasta.

If you have pasta boiling around the same time, reserve the water after draining the pasta. 

This salty, starchy water will thicken up your pesto sauce. 

You can use pasta water in the following manner:

  1. Add a small quantity of pasta water at a time; mix and check the consistency. This will help in binding and emulsifying the sauce,
  2. Toss in the pasta to the sauce. The pesto is evenly distributed and coats the pasta. 

But make sure to not add a lot of pasta water, or it’ll make a thick sauce runny, and you will have to start the thickening process again.

Thickening With Cornstarch

Cornstarch is commonly found at home and is a great thickening agent. 

Cornstarch is made into a slurry before adding to pesto. This will prevent clumping. The steps are described under.

  1. Add a 1:1 ratio of cornstarch and liquid (cold water or vegetable broth) in a bowl,
  2. Mix until it becomes a smooth slurry,
  3. Pour this slurry into your sauce while stirring,
  4. Cook over a gentle heat, stirring constantly until the sauce reaches your preffered consistency.

Add in only a little slurry at a time to avoid over-thickening of the pesto sauce.

Alternatively, you can also use potato starch or tapioca starch instead of cornstarch.

Use this option as your last resort because starches can mask the delicate flavor and aroma of pesto sauce.

Other Suggestions To Avoid A Watery Pesto Sauce

If your pesto sauce isn’t thick enough, take a deep breath. You need to check if you are following the recipe accurately. Since the pesto contains such few ingredients, each one (and their ratio) matters tremendously. 

Use High-Quality Ingredients

Ensure that you use fresh and good-quality ingredients.

There is no cooking involved in this recipe, so it’s just about the art of mixing ingredients.

Add Ingredients Slowly

For the right consistency, do not just dump all the ingredients in the food processor at once and start pulsing them. 

Instead, pulse the pine nuts and garlic with slow addition of olive oil first and then add chopped basil leaves and pulse again and check for the desired thickness. 

The sequence of addition of ingredients is critical here.

Consider Blanching

A quick blanching step before pulsing the basil helps in the emulsification of the leaves, keeping your pesto smooth and full-bodied. 

Blanching also enhances the bright green color of the pesto. 

Remember to use an ice water bath immediately after the leaves are blanched.

Refrigerate 

Before you try anything else, and if you have time, refrigerating the pesto for about an hour or so will help thicken it.

Finally

Pesto is amazing; when it is done right!

It needs to be relatively thick, and it needs to coat the pasta without sliding off!

Thankfully, as you can see, there are many ways to save a runny pesto should you find yourself in the unfortunate position of a thin sauce.

Your choice of method, however, will depend on the ingredients and the time you have available.

Want to learn how to thicken other similar sauces? Then go ahead and check out my other related guides: