Prep 15 mins
Cook 2 hrs 10 mins
Cooling Time 20 mins
Total 2 hrs 45 mins
Serves 8 to 10 servings
Makes 6 cups
Ingredients
- 4 large moist sweet potatoes (4 pounds; 1.8 kg), such as ruby or garnet yams (about 4 large potatoes; see notes)
- 8 (6-inch) sprigs fresh thyme, divided
- 6 tablespoons unsalted butter (3 ounces; 85 g)
- 1/4 cup (60 ml) maple syrup
- 1/2 teaspoon Diamond Crystal kosher salt; for table salt, use half as much by volume
Directions
- Adjust oven rack to middle 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 and 3 sprigs of thyme. 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 some resistance, 1 hour 30 minutes to 1 hour 45 minutes. Carefully unwrap and discard foil and thyme sprigs and place unwrapped potatoes in even layer on same sheet pan. Increase oven temperature to 400°F (205ºC), and roast until sweet potatoes are caramelized and a thin skewer inserted into potatoes meets no resistance, about 30 minutes. Remove potatoes from oven and set aside until cool enough to handle, about 20 minutes.
- While sweet potatoes are cooling, melt butter in a medium saucepan over medium-low heat, swirling gently, until particles are pale golden brown and smell nutty, about 10 minutes. 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 (1/4 teaspoon), and add to bowl with butter and maple syrup.
- Peel sweet potatoes and discard skins and any juices. Add flesh to bowl with butter mixture.Beat with whisk attachment or a handheld mixer on medium-low speed until smooth and fluffy, about 2 minutes. Season to taste with salt. Serve. See note for make-ahead suggestions.
Special Equipment
- Rimmed baking sheet
- Handheld electric mixer or stand mixer
Notes
Sweet potatoes can be made even sweeter by pretreating them in a water bath to activate their enzymes. To do this with a sous vide–style circulator, set your circulator for 145°F (63°C). Place the sweet potatoes directly in the water bath and let circulate for 2 to 4 hours before proceeding with the recipe, if doing sous vide potatoes, cut unwrapped potatoes in half lengthwise before returning to roast at 400°F. To do this with a beer cooler, fill your cooler with water at 170 to 175°F (77 to 79°C). Add the potatoes, cover, and let rest for 2 to 4 hours before proceeding.
Make-Ahead and Storage
Sweet potatoes can be refrigerated for up to 5 days. To store and reheat, transfer the sweet potatoes to a heavy-duty zipper-lock bag with the air pressed out. Reheat by completely submerging the 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. The best way to do this is with a sous vide–style circulator set at 150°F (66ºC).
