Mashed potatoes seem like something that should be easy to get right. After all, they are just potatoes, butter, milk and salt, with optional additional flavorings like herbs, garlic, cheese and spices tossed in as desired.
But like many foods, potatoes are more complex when you take a closer look. The inside of a potato is basically a lot of little sacs containing starch. Many, but not all of these will swell and burst while the potatoes are cooked, which contributes to mashed potatoes' fluffy texture.
Breaking too many of those sacs releases too much starch, making the mashed potatoes "gluey" rather than fluffy. This is why it's a no-no to use electric devices like a hand mixer, food processor or blender to mash or "whip" potatoes, especially if you're making mashed potatoes with russet potatoes, which are higher in starch than other potatoes. You want the gentler processing achieved by hand tools like a potato masher or, my preference, a ricer, which looks like an oversize garlic press.
The other trick is to add the butter before the milk, as adding the fat first coats the starch and makes for better texture (or so Cook's Illustrated recommends, and they are usually right). This recipe is from adapted from BonAppétit, applying these key principles for making optimally delicious mashed potatoes.
Buttery Mashed Potatoes
Adapted from a recipe by Bon Appétit
4 lbs. Yukon Gold potatoes, peeled and cut into 2” pieces
1 tbsp. kosher salt, plus more
1½ cups whole milk
3 sprigs thyme (optional)
2 bay leaves
¾ cup (1½ sticks) unsalted butter, plus more for serving
1. Place potatoes in a large pot and add enough cold water to cover by about an inch. Add salt and bring to a boil over high heat. Reduce heat to medium-low and simmer until potatoes are very tender but not saturated or crumbly, about 20–25 minutes.
2. Drain potatoes and return the potatoes to the pot and set it over low heat. Gently stir until the potatoes are dry, about 1 minute.
3. Heat milk and herbs in a small saucepan over medium heat until the mixture is warm (do not let it boil). Remove from heat.
4. Pass the hot potatoes through a ricer into a large bowl (if allowed to cool, the potatoes will become gummy). Add butter and stir with a wooden spoon to combine with the potatoes.
5. Remove herbs from the warm milk mixture and discard. Gradually add milk mixture to potatoes, stirring vigorously with a wooden spoon until combined and smooth; season with salt.
6. Serve mashed potatoes with a few pats of butter on top.