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How To Fix Runny Mashed Potatoes | The Best Way

This article will answer several questions about how to fix runny mashed potatoes, including whether allowing them to cool or adding butter will thicken them. I will also address the use of different thickening agents and other methods.

The best way to fix runny mashed potatoes is to cook them more. You can do this on the stovetop over low heat, stirring occasionally, or in the oven in a shallow dish at 300°F (149°C). You can also microwave on high for 1 minute at a time. Cook uncovered to allow evaporation of the excess water.

Please read on to learn all the details. 

Will Mashed Potatoes Thicken as They Cool?

Mashed potatoes will thicken a little as they cool due to evaporation. However, runny mashed potatoes need extra cooking, straining, or an added thickening agent like corn starch. You can also add parmesan cheese, more potatoes, or dehydrated potato flakes. 

Remember that overcooking or over-stirring your mashed potatoes will cause them to become gluey and unpleasant. If your mashed potatoes are very runny, try adding a thickener instead of cooking them more.

Will Butter Thicken Mashed Potatoes?

Butter will not thicken runny mashed potatoes. It will make them runnier. However, adding it to thickened mashed potatoes will improve the texture. The protein and added fat will make the potatoes fluffier, smoother, and richer in flavor. This is why mashed potato recipes often call for dairy.  

However, don’t add butter to runny mashed potatoes! Wait until you have thickened the mash before adding butter or cream. It may not have the desired effect on the texture if the potatoes have too much water, making them runnier. 

In addition, if you do add butter to your mashed potatoes, don’t melt it first. Milk or cream should be warmed before you add them, but butter should be added cold, one tablespoon (15 ml) at a time. Allowing butter to melt into hot mashed potatoes helps the fat and proteins distribute evenly for that perfect fluffy, smooth texture.

Related How To Fix Undercooked Mashed Potatoes | The Best Way.

What Are the Best Thickeners To Fix Runny Mashed Potatoes?

The best thickeners to fix runny mashed potatoes include corn starch, flour, or powdered milk. However, each has a different thickening power and effect on the texture and flavor of your potatoes. 

  • Corn starch is the best choice. It thickens twice as better as flour and has little to no effect on flavor. 
  • Flour (all-purpose) is also a great choice when your mashed potatoes are only a little runny. However, it will add a chalky flavor if you use too much. You can avoid this by adding the flour while cooking your mashed potatoes over low to medium heat for a few minutes, but be careful not to overcook. Cooking the flour will eliminate its chalkiness, but you don’t want to overcook your potatoes in the process!  
  • Powdered milk will thicken your potatoes as well as flour while adding a rich and creamy flavor. Keep in mind it increases the protein and calorie content. In addition, dairy products will shorten the keeping time of your leftover mashed potatoes and make them more susceptible to spoiling if left out of the fridge too long. 

Other Thickeners To Fix Runny Mashed Potatoes

While cornstarch, flour, and powdered milk are the best and handiest choices, if you don’t have any, you can use numerous other thickeners. Any starch will work, including:

  • Potato
  • Rice
  • Tapioca

Arrowroot (kuzu or kudzu) is another high-quality thickening agent that works similarly to corn starch and adds no extra flavor.

You can also use corn flour or rice flour, but again, the flour will alter the flavor. Cooking the flour in the mashed potatoes will improve its flavor but may only partially eliminate it. This is especially true the more flour you use. 

Finally, gelatin powders like agar agar, guar gum, xanthan gum, or pectin are other common thickeners you can use in a pinch. However, they will alter the texture significantly when applied in large quantities, making your potatoes gluey.

How To Add Thickener to Runny Mashed Potatoes

Whatever thickener you choose, add a little at a time and stir thoroughly with a fork before adding more. 

For small batches of 6 servings or less, start with one teaspoon (5 g) thickener at a time. Add ½ to 1 tablespoon (7-15 g) at a time for larger batches. This will help to avoid over-thickening. In addition, make sure your potatoes are still warm when you add the thickener, as this will help it dissolve more quickly.

A woman sifting thickener into a bowl

If you do add too much thickener, don’t worry! Your mashed potatoes can be fixed by adding more moisture. Stir in 1 tbsp (15 ml) of water at a time until you reach the desired consistency.

You can also add butter or milk in place of water, as these will add that creamy richness and improve the texture of your mashed potatoes.

Related 11 Yummy Substitutes for Milk in Mashed Potatoes.

What Are Ways To Fix Runny Mashed Potatoes Without Thickeners?

One way to fix runny mashed potatoes without thickeners is to strain them using cheesecloth. Another is to add more potatoes, preferably Idaho or russet, because they are very starchy and will absorb excess water. You can also add dehydrated potato flakes or grated parmesan cheese.

As I mentioned above, cooking mashed potatoes more is also a suitable method that requires no extra tools or ingredients. However, the methods detailed below are great if you want to avoid overcooking your potatoes and ending up with an unappetizing, gluey consistency. 

Strain Your Mashed Potatoes 

This method is best for small batches. 

  1. Position a large piece of layered cheesecloth into a clean cooking pot. You want as many layers as possible to prevent your potatoes from squeezing through! Make sure the cheesecloth rests fully against the bottom of the pot while the edges hang over the rim. 
  2. Next, pour the mashed potatoes into the cheesecloth and twist the edges together over the top. 
  3. Squeeze the water out of the potatoes and into the pan. Place the drained potato into a serving dish or another pot. Voila! No more runny potatoes. You can even save the potato water to make gravy or soup

Add More Potatoes

This is another method that won’t compromise the taste or texture of your mashed potatoes. If you have extra potatoes, cook them up and add them to your runny mash. For best results, use russet or Idaho potatoes because these are especially starchy. Other potatoes, like red-skinned varieties, have less starch and will not absorb the excess water. 

It’s also crucial that you avoid boiling your potatoes. Simmer them instead, as this will reduce the chance of them breaking apart in the water, resulting in another batch of runny potatoes. You can also bake the potatoes for a few minutes after simmering them to eliminate excess moisture. Take them out when the edges start to turn white. 

Finally, mash the potatoes with no extra moisture added before you mix them into your runny batch. The extra potatoes should absorb all the excess water, leaving you with perfect mashed potatoes. 

Add Dehydrated Potato Flakes

Some people prefer to avoid reconstituted potatoes, which can be a little grainy and tasteless. However, adding a small amount to your fresh mashed potatoes usually doesn’t compromise the taste or texture noticeably. In addition, you can combat the graininess by adding some dairy, such as cream or butter.

  1. Add the dehydrated potato 1 tablespoon (30 g) at a time and mix thoroughly before adding more. It takes a minute or two for the flakes to rehydrate completely. The flakes will absorb the excess water and make the mash a little lighter.  
  2. Add more salt and seasoning, as dehydrated potatoes often contain none.

Add Grated Parmesan Cheese

Adding fresh parmesan cheese is an excellent way to thicken your runny mashed potatoes while adding flavor and improving the texture. You don’t have to use parmesan, but hard cheeses are best (e.g., Asiago or Romano). They contain little moisture and carry a strong flavor that compliments potatoes well. 

  1. To thicken your potatoes, first, grate the cheese. The finer you grate the cheese, the smoother and creamier the texture! 
  2. Add the grated cheese to hot mashed potatoes, one tbsp (15 g) at a time, and mix thoroughly until melted. Take care not to add too much because hard cheeses are high in salt! 
  3. After mixing in each tablespoon (15 ml) of cheese, do a taste test. You don’t want to overload your mashed potatoes. You may need to combine this method with another if your mash is particularly runny. 

Final Bite

The best way to thicken runny mashed potatoes is to cook them longer or add cornstarch. Other thickeners include all-purpose flour and powdered milk, but you can use potato starch, tapioca, arrowroot, etc. Other types of flour will also work. 

You can strain your runny potatoes with cheesecloth or add more potatoes (either fresh or dehydrated). Parmesan cheese makes an excellent thickener in addition to adding richness and flavor. 

Finally, add thickeners no more than one tablespoon (15 g) at a time. Add starches (i.e., corn starch, tapioca, arrowroot) 1 teaspoon (5 g) at a time.