Butternut squash has dense, creamy, sweet flesh that you can easily scrape from the skin after baking. Purée it with sautéed onions and broth to make a silky, pumpkincolored soup, then stir in some minced chipotle chiles to warm it up. Garnish with a flurry of grated Cotija cheese—a hard, well-aged cow’s milk cheese sold in Mexican markets—and a sprinkle of toasted pumpkin seeds.
Preheat the oven to 350°F.
Cut the squash in half, then cut each half in quarters. Scoop out and discard the seeds and pulp. Rub the squash pieces with 2 tablespoons of the olive oil and set on a roasting pan, cut side up. Sprinkle with ½ teaspoon of the salt. Roast, turning the pieces several times, for about 1 hour, until the squash is easily pierced with a fork. Allow the squash to cool, then scoop the tender flesh from the skins. Set aside.
Heat the butter with 1 tablespoon of the remaining olive oil in a large saucepan over medium heat. Add the apple and cook for 3 to 4 minutes, until partly tender but not browned. Add the onion and cook for 3 to 4 minutes longer, until the onion is tender.
Stir in 2 cups of the chicken stock and simmer until the apple is fully tender, about 5 minutes. Stir in the pumpkin, orange zest, orange juice, brown sugar, nutmeg, mace and remaining 1 teaspoon salt. Add the remaining 3 cups stock and simmer for 15 minutes.
Dice enough of the roasted squash to make 1½ cups and set aside. Coarsely chop the remaining squash and add to the soup. Cook over medium-low heat for 15 minutes. Add the milk and simmer 5 minutes longer. Allow to cool slightly. Working in batches, purée the soup in a blender or food processor until very smooth, returning the soup to the pot. Gently reheat the soup over medium-low heat.
Just before serving, heat the remaining 1 teaspoon olive oil in a small skillet over medium heat. Add the pumpkin seeds and toast, stirring often, for 1 to 2 minutes, until crisp and lightly browned (be careful, the seeds may pop out of the pan). Spoon the seeds onto a small plate to avoid burning.
Heat the reserved diced squash in a microwave for 30 seconds or warm in a small saucepan with 1 cup of the soup over medium-low heat. Spoon the diced squash into warmed soup bowls and ladle the hot soup over. Top each bowl with toasted pumpkin seeds and a few grains of sea salt.
