If you do – just soak them for 5 minutes and rinse. Doing so is a science thing – soaking cut potatoes removes excess potato starch. This means fluffy mashed potatoes (and not gluey!)
The result is very fluffy mashed potatoes. (If you decide to try soaking the raw potatoes anyway, they can be soaked in water in the refrigerator for several hours without any safety concerns. Potatoes can be soaked even overnight as long as they are in the refrigerator.)
Potatoes can be peeled prepped and cut into water up to 2 days before boiling for mash.
How long do you need to soak potatoes? Soaking potatoes for 15 to 30 minutes is sufficient, but you can soak them for up to an hour, if you have other things to do around your kitchen.
Give them a cold water bath: Once your potatoes are chopped, toss them into a large bowl. Then cover the potatoes completely with cold water and let them soak for at least 30 minutes (or up to overnight). This will help to rinse off the excess starch and help the potatoes crisp up beautifully in the oven.
Doing so is a science thing – soaking cut potatoes removes excess potato starch. This means fluffy mashed potatoes (and not gluey!)
Soaking potatoes in water helps remove excess starch. Excess starch can inhibit the potatoes from cooking evenly as well as creating a gummy or sticky texture on the outside of your potatoes. Cold water is used because hot water would react with the starch activating it, making it harder to separate from the potatoes.
We usually recommend no more than 24 hours. You can keep the potatoes from absorbing the water by making sure the water is not salted, and is chilled (you can even add ice to the water). To keep the potatoes from turning black from oxidation, add 1 teaspoon of lemon juice or white wine vinegar to a gallon of water.
They just won't stand up to an overnight soak, so don't do it. The larger the potato pieces, the longer they'll last in water. If you're prepping with smaller pieces, don't soak for more than 12 hours. This trick is handy, but it'll only work for about 24 hours — so don't prep too far in advance.
Soaking potatoes in cold water helps get rid of the starch, which makes them crispier. The sugar in the brine prevents them from soaking up too much oil when fried, which also makes them crisp.
If you first boil water and then add potato pieces, you'll have a less than ideal texture in the end. The sudden bath of boiling water will quickly cook the outside of the spuds while leaving the inside uncooked. Instead, add all your potato cubes to a pot, and fill it with water just over the top of the potatoes.
Under-Seasoning the Potatoes
Potatoes are, by nature, really starchy, and starches require a decent amount of salt to taste good. Adding tons of salt to the water your potatoes boil in is necessary to get the seasoning inside the spuds.
Cover the pot and simmer until potatoes are tender — about 15 to 20 minutes. A knife tip inserted into a potato should meet no resistance; if the potato clings to the knife, the potatoes need to cook longer. When potatoes are done, remove from heat and drain immediately.
Dissolve the salt in a large bowl filled with warm water. Wash but do not put holes in the potatoes. Add potatoes to the salt water so they are completely submerged. Soak for a minimum of 2 hours.
Remove the potatoes from the soaking water, place them in a towel and squeeze out as much moisture as possible. Allow the water to rest for about 30 minutes so the starch settles. Pour the water out of the bowl, leaving the starch at the bottom of the bowl. Combine the starch and potatoes just before cooking.
Cubed spuds will take around 15 minutes where larger chunks or whole new potatoes will be 20-25 minutes. To check when they are done, pierce the potatoes with the tip of a knife to see how much resistance there is. If it goes in easily, you're done!
Peeled potatoes left out by themselves at room temperature, on a refrigerator shelf or wrapped in foil or plastic wrap will still get dark overnight, so submerge them in a bowl of water, cover and refrigerate. Cubed peeled potatoes can sit in water overnight, but they need to be refrigerated.
You can do nearly everything — boil, peel, and mash; stir in milk and salt — up to two days ahead. Before serving, reheat. Adding butter at the last minute makes them taste freshly mashed.
First let's talk about why cut potatoes need to be immersed in water to begin with. The reason is to prevent the potatoes exposure to air, which causes dehydration, oxidation, and discoloration. Immersing cut potatoes will also help rinse off excess starch.
For the fluffiest and lightest mashed potatoes, use Russets and rinse off excess potato starch before and after cooking.
Potatoes will be firmer and crispier if you soak them in salt water before frying or cooking. Although it may seem like an extra step, this process will help you prepare the potatoes in advance.
Prepping the potatoes ahead of time
To save time on peeling and chopping on Thanksgiving Day (or any other day that includes mashed potatoes), you can peel the spuds and keep them submerged in a bowl of water in the fridge, whole or cut up, for hours — even overnight — before boiling.
Here's how to do it: For every pound of potatoes in your mash, drizzle 1 tablespoon of melted butter over the dish and fold it gently into the potatoes. If the mash is still too gluey for your liking, repeat the process with another tablespoon of butter.
Mashed potatoes tip #1:
Always start cooking potatoes in cold water. Don't plop them into boiling water. Cook them at a modest simmer for about 20 minutes and they will have a smoother end texture and cook more evenly.
Too much whipping (or mashing) will give you sticky — not fluffy — mashed potatoes. Make the best of it and turn them into cheesy mashed potato cups: Mix the potatoes with grated cheddar and an egg, then scoop the mixture into lightly greased muffin cups.