How to Thicken Mashed Potatoes (7 Simple Ways)

Here are some quick and easy ways to thicken your mashed potatoes. Even if they started out a bit runny!

When it comes to sides, there’s nothing like some good old mashed potatoes. They’re super simple to make but also super delicious and an excellent pair for many main dishes.

But, not all mashed potatoes are created equal. I love mine to be rich, smooth, buttery, and most importantly, thick!

Nobody likes soggy, soupy mashed potatoes. But if you’ve made them a little too runny for your taste, don’t worry! You don’t have to throw them out just yet.

To thicken mashed potatoes, you can add a thickening agent like cornstarch, flour, powdered milk, or tapioca. Add one tablespoon at a time until you reach your desired consistency.

You can also add heat, more potatoes, or even strain the mashed potatoes in order to reach your desired consistency.

Here are 7 different ways to save your mashed potatoes and make them the best and thickest you’ve ever had.

How to Thicken Runny Mashed Potatoes

1. Add a Thickening Agent

If you have flour, cornstarch, or powdered milk on hand, you can thicken up your mashed potatoes in a jiffy!

In fact, cornstarch has 2x more thickening power than flour, so that’s usually my go-to. But either will work.

Add one tablespoon at a time, until you reach your desired consistency. Be sure to mix well before adding another tablespoon.

Important Note when using cornstarch: Don’t overstir! Once the mashed potatoes are nice and thick, let it set. Any further agitation can cause the cornstarch to thin.

Also, make sure your runny mashed potatoes are warm so that it fully dissolves into the mixture.

2. Heat on a Stovetop

One way to thicken mashed potatoes is to add more heat. In a large pot, heat the runny potatoes over low to medium heat. Stir occasionally to prevent it from sticking to the bottom of the pot.

Follow these tips when heating on a stovetop.

• When stirring runny mashed potatoes, use a fork instead of a spoon or a ladle. This helps to avoid too much stirring and will allow excess liquid or moisture to evaporate more quickly.
• Be careful not to stir too much! Overworking the potatoes can ruin the texture and make it too sticky or even gluey.
• Don’t cover the pan! You might think that more heat will thicken the potatoes faster but we actually want excess moisture to have room to escape so keep the pot uncovered.

3. Heat in an Oven

Another way to thicken mashed potatoes is by baking it in an oven as adding heat allows the excess liquid to dissolve or evaporate.

Follow these steps to save your potatoes.

• Preheat your oven to 300F.
• Once your oven is heated, place the mashed potatoes in an uncovered bowl or pan.
• Bake your potatoes for 15 minutes or until all the excess moisture has dried out.

4. Heat in a Microwave

Here’s a quick and easy tip. For thicker mashed potatoes, simply pop them in the microwave for a few minutes.

Here’s how to do it.

• Place your mashed potatoes in an uncovered bowl and microwave on high for 1 minute. Make sure your container is microwave safe!
• After a minute, take out the bowl to lightly stir and check if there is less moisture.
• Repeat these steps until your potatoes are in the desired consistency.

Keep in mind that although this might be the quickest way to thicken the potatoes, you can only use this method for smaller amounts.

5. Strain

Another way to reduce the moisture in runny mashed potatoes is by straining. All you need is a cheesecloth and a strainer.

Follow these steps when straining.

• Take a cheesecloth and pour your soupy potatoes in.
• Tie the ends of the cheesecloth together tightly to remove moisture and form a ball of potato.
• Place the cheesecloth over a strainer and leave for up to an hour.
• Take out your strained and thick potatoes and serve!

After straining the potatoes, it’s also a good idea to take the extra step of reheating them on a stovetop, oven, or microwave. This ensures that all extra moisture has dissolved and you can serve the matched potatoes warm!

Make sure to save the drained liquid. You can use it to make gravy or soup… Nothing goes to waste!

6. Add More Potatoes

If you have extra potatoes, adding them to runny mashed potatoes will definitely thicken the consistency and might even make it taste better.

Here’s the best way to add potatoes.

• Grate or shred your potatoes.
• Cook the shredded potatoes in a pan to soften them.
• Once softened, set aside to cool before draining with a cheesecloth and strainer.
• Mash your potatoes with a fork.
• Add this to the runny mashed potatoes.

Depending on how much potato you added, you may need to reheat. If you added a small amount, definitely heat everything again so you can enjoy your new and improved thick potatoes warm!

7. Add Parmesan or Hard Cheeses

If you want to improve not only the texture of your mashed potatoes but the taste as well, adding flavorful thickening agents like cheese will definitely do the trick.

Parmesan is an excellent thickening agent. It has a versatile flavor that matches many other dishes including mashed potatoes. Pecorino is also a great option if you’re looking for an even stronger, more savory flavor.

With any cheese you add, make sure they are finely grated if you want the texture to be thick but also smooth.

How to Avoid Runny Mashed Potatoes

Taking all these extra steps to fix runny mashed potatoes can be quite time-consuming, especially when you’re hungry!

The next time you make this delicious side dish, keep these steps in mind for the perfectly thick and fluffy potatoes.

• Use the right potatoes! For the best texture, use Yukon gold or Russet potatoes.
• Start with cold water! When cooking your potatoes, start with cold water instead of placing them directly in boiling water. This will help them to cook more evenly.
• Drain before adding other ingredients! After boiling your potatoes, make sure to drain them thoroughly before adding other ingredients, especially liquid.
• Don’t underwork or overwork you potatoes! Not stirring enough will cause mashed potatoes to be too liquidy and stirring too much will make them stiff and starchy. So be gentle with your potatoes to keep them thick and fluffy.