Why It Works
- Par-cooking the potatoes in 160°F water enhances the development of simple sugars, leading to sweeter and more flavorful roast potatoes.
- Roasting the potatoes on aluminum baking sheets conducts more heat to them, browning and crisping them better and faster.
An intense brown butter that's enriched with reduced chicken stock, infused with woodsy rosemary, and brightened with lemon juice adds incredible flavor to these intensely sweet roasted sweet potatoes.
- 3 pounds (1.4kg) sweet potatoes, peeled and cut into 1/2-inch chunks
- 3 tablespoons (45ml) vegetable or canola oil
- Kosher salt and freshly ground black pepper
- 1/2 packet unflavored gelatin (about 1 1/4 teaspoons; 4g)
- 1/4 cup (60ml) homemade or store-bought low-sodium chicken stock
- 1 stick unsalted butter (8 tablespoons; 115g)
- 3 rosemary sprigs
- 1 teaspoon (5ml) fresh juice from 1 lemon
Place sweet potatoes in a large saucepan and cover with cold water. Heat water to 160°F (70°C) as registered on an instant-read thermometer. Cover and set aside for 1 hour.
Adjust oven racks to upper-middle and lower-middle positions and preheat oven to 400°F (200°C). Drain sweet potatoes and transfer to a large bowl. Toss with oil and season to taste with salt and pepper. Spread sweet potatoes on 2 rimmed baking sheets and roast until bottom sides are browned, about 30 minutes. Carefully flip potatoes with a thin spatula and roast until second side is browned and potatoes are tender, about 20 minutes longer.
Meanwhile, in a small container, sprinkle gelatin over chicken stock and let bloom for 5 minutes. Microwave until gelatin is dissolved, stopping and stirring as needed to help it dissolve, about 2 minutes.
In a small saucepan, melt butter over medium-high heat until foamy. Continue to cook, swirling pan, until milk solids in butter turn a deep hazelnut brown, 1 to 2 minutes. Remove from heat and add rosemary (don't be alarmed; butter will foam and fizzle when rosemary is added), swirling to coat.
Add chicken stock to butter, return to medium heat, and bring to a simmer. Cook, swirling, until stock reduces slightly and sauce becomes rich and silky, about 3 minutes. Remove from heat, discard rosemary, and add lemon juice. Season with salt.
In a mixing bowl, toss potatoes with butter sauce and serve. Potatoes can be made in advance, tossed with sauce, and set aside until ready to serve; rewarm in the oven before serving.
Aluminum rimmed baking sheets, instant-read thermometer