Oops, My Mashed Potatoes are Soupy. Here's How to Thicken Them
When it comes to perfect mashed potatoes, the best defense is a good offense, so let's review the basics.
- Use the right kind of starchy potato that turns soft and fluffy when cooked, such as russet or Yukon gold, instead of waxy varieties, such as red-skinned new potatoes.
- Cook the potatoes only until tender when pierced with a fork instead of over-cooking them until they begin to fall apart and turn soggy.
- Drain the potatoes in a colander and then let them stand until the surface water evaporates away, about 3 minutes. They'll stop streaming vigorously and the edges will look a bit chalky. But don't let them stand so long that they turn cold. Potatoes should be mashed and seasoned while warm.
- Don't mash potatoes with anything you have to plug in. That means no mixers, food processors, or blenders that will turn the potatoes gluey. For smooth puree, use a food mill or potato ricer. If you don't mind a more rustic texture, use a hand-held potato masher or crush them with a large wooden spoon.
- Add the liquid (such as milk, half-and-half, or cream) gradually. Make sure it's warm instead of straight out of the fridge, and stir only until blended. It's far easier to add more liquid than to correct a wet mess.
If the potatoes turn out too runny, despite these guidelines, try one of these tricks.
- Transfer the potatoes into a shallow container and place them in a 325°F oven to dry out for 10 to 15 minutes. This works better than trying to cook out the excess moisture on top of the stove in a saucepan that will need to be stirred to keep the potatoes from scorching on the bottom.
- Cook more potatoes and mash them properly (see steps 2 to 4 above) but with no additional liquid, and then fold them into the runny batch.
- Stir in dehydrated mashed potato flakes a tablespoonful at a time until you reach the right consistency. The flavor and texture of instant mashed potatoes doesn't suit everyone, but they can save the day and can work wonders in this case.
- Whisk a little cornstarch into the warm potatoes, only a teaspoon at a time, until the potatoes thicken to your liking. The potatoes must be warm. You can also use tapioca starch or potato starch, although most cooks are less likely to have those products on hand. Don't use flour; it won't lose its raw taste in the heat of the potatoes without lots more cooking and stirring, which trades one problem for another.