The Best Mashed Sweet Potatoes Recipe

The Food Lab

Unraveling the mysteries of home cooking through science.

The Best Mashed Sweet Potatoes Recipe

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

Have you ever wondered why sweet potatoes are so darn insecure? It's time to say good-bye to the days of hiding sweet potatoes behind 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 It Works

  • Browning butter packs in tons of flavor, without dulling the sweet potatoes.
  • Slow-roasting the sweet potatoes activates endogenous enzymes that bring out their natural sweetness.
  • A touch of maple syrup and a bit of chopped thyme are the only embellishments these naturally sweet sweet potatoes need.
  • Yield:Serves 8 to 10
  • Active time: 20 minutes
  • Total time:2 hours 20 minutes


  • 4 pounds (1.8kg) moist sweet potatoes, such as ruby or garnet yams (about 4 large potatoes; see note)
  • 8 sprigs thyme, divided
  • 6 tablespoons butter (3 ounces; 85g)
  • 1/4 cup (60ml) maple syrup
  • Kosher salt


  1. 1.

    Adjust oven rack to center position. Place 2 large sheets of heavy-duty aluminum foil on a work surface. Working with 1 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 oven. Set oven to 300°F (150°C). Roast until a thin skewer inserted into potatoes meets no resistance, about 2 hours. Remove potatoes 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 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 whisk attachment or a handheld mixer until smooth and fluffy, about 2 minutes. Season to taste with salt. Serve. See note for make-ahead suggestions.