The Best Mashed Sweet Potatoes Recipe

The Food Lab

Unraveling the mysteries of home cooking through science.

J. Kenji López-Alt
The Best Mashed Sweet Potatoes Recipe
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  • Yield:Serves 8 to 10
  • Active time:20 minutes
  • Total time:2 hours 20 minutes
  • Rated: 4.0
This recipe appears in:
The Food Lab: For the Best Mashed Sweet Potatoes, Use Science, Not Sugar

A science-based approach of getting the best out of your sweet potatoes. [Photographs: J. Kenji Lopez-Alt]

Have you ever wondered why sweet potatoes are so darn insecure? It's time to say good bye to the days of sweet potatoes having to hide behind a mask of sugar and bolted-on marshmallows. What we have here is a technique for making mashed sweet potatoes that are so sweet, rich, and packed with sweet potato flavor, they need only the simplest of embellishments to shine.

Why this recipe works:

  • Browning butter packs in tons of flavor without dulling the sweet potatoes.
  • Slow-roasting the sweet potatoes activates endogenous enzymes that make bring out their natural sweetness.
  • A touch of maple syrup and a bit of chopped thyme is the only embellishment these naturally sweet sweet potatoes need.

Note: Sweet potatoes can be made even sweeter by pre-treating them in a water bath to activate their enzymes. To do this with a sous vide-style circulator, set your circulator for 150°F. Place the sweet potatoes in the water bath and let circulate for 2 to 4 hours before proceeding with recipe. To do with a beer cooler, fill your cooler with water at 170 to 175°F. Add the potatoes, cover, and let rest for 2 to 4 hours before proceeding.

To make ahead: Sweet potatoes can be refrigerated for up to 5 days. To store and reheat, transfer sweet potatoes to a heavy duty zipper-lock bag with the air pressed out. Reheat by completely submerging zipper-lock bag in a pot full of hot (not boiling) water, removing the bag occasionally to squeeze contents around until fully reheated. About 30 minutes. I reheat mine with a sous vide-style circulator set at 150°F.

Ingredients

  • 4 pounds moist sweet potatoes such as ruby or garnet yams (about 4 large potatoes, see note above)
  • 8 sprigs thyme, divided
  • 6 tablespoons butter
  • Kosher salt
  • 1/4 cup maple syrup

Directions

  1. 1.

    Adjust oven rack to center position. Place two large sheets of heavy duty aluminum foil on a work surface. Working one sheet at a time, place half of potatoes in center along with 3 sprigs of thyme. Fold up foil and crimp edges to seal tightly. Repeat with other half of potatoes. Transfer pouches to a rimmed baking sheet and place in the oven. Set oven to 300°F. Roast until a thin skewer inserted into the potatoes shows no resistance, about 2 hours. Remove from oven and set aside until cool enough to handle.

  2. 2.

    Meanwhile, melt butter in a medium saucepan over medium-low heat, swirling gently until particles are pale golden brown and smell nutty. Immediately transfer to a large bowl or the work bowl of a stand mixer fitted with a whisk attachment. Add maple syrup. Pick leaves off of remaining 2 thyme sprigs, roughly chop, and add to bowl.

  3. 3.

    Peel sweet potatoes and discard skins. Add flesh to bowl with butter and syrup. Beat with the whisk attachment or a handheld mixer until smooth and fluffy, about 2 minutes. Season to taste with salt. Serve. See note above for make-ahead suggestions.

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