3 pounds (1.4kg) sweet potatoes, peeled and cut into 1/2-inch chunks
5 tablespoons (75ml) vegetable or canola oil
Kosher salt and freshly ground black pepper
1/2 teaspoon (2g) ground cumin
1/2 teaspoon (2g) ground coriander seed
1/2 teaspoon (2g) chipotle powder
1 cup crushed pecans (6 ounces; 170g)
1 tablespoon (15g) light brown sugar
1 teaspoon minced sage leaves (about 5 leaves)
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 3 tablespoons (45ml) 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 skillet, combine remaining 2 tablespoons (30ml) oil with cumin, coriander, and chipotle powder and cook over medium-high heat, stirring and swirling, until spices are fragrant and toasty, 1 minute. Add pecans and toss to coat with spiced oil. Continue cooking until pecans are lightly toasted, 1 minute. Sprinkle brown sugar on top and stir until well combined and melted, about 1 minute. Season with salt.
In a large mixing bowl, combine potatoes, spiced pecans and their oil, and minced sage and toss to combine. Serve right away, or set aside until ready to serve and reheat before serving.