2 pounds kabocha, pumpkin, or butternut squash
1 pound sweet potatoes
4 cloves garlic, peeled
3 tablespoons olive oil, divided
Freshly ground black pepper
1 shallot, chopped
2 teaspoons freshly grated ginger
3 tablespoons mellow white or yellow miso (gluten-free if necessary)
6 cups vegetable stock
2 tablespoons chopped chives or scallions
1/2 teaspoon shichimi togarashi or black and/or white sesame seeds
Preheat oven to 450°F.
Seed the pumpkin and cut it into 2-inch pieces. If the pumpkin is easy enough to peel raw, such in the case of a butternut squash, you can go ahead and peel it before cutting and roasting. A pumpkin with a harder skin, such as a kabocha, may be cut and roasted and the peel removed afterwards. (Or simply leave the skin on; it's edible when tender, although the soup will be slightly less smooth.)
Peel and cut the sweet potatoes into 2-inch pieces.
Combine the pumpkin, sweet potatoes, and garlic on a baking sheet, toss with 2 tablespoons of olive oil, and sprinkle with salt and pepper. Roast in the oven until the pumpkin and sweet potatoes are tender when pierced with a knife, about 30 minutes, tossing halfway through. If you left the pumpkin skins on, peel when cool enough to handle.
Heat the remaining tablespoon of olive oil in a large pot over moderate heat. Add the shallots and ginger and cook until softened. Add the miso and vegetable stock and stir until dissolved. Add the roasted vegetables and simmer for 15 minutes. Turn down the heat if necessary to avoid boiling, as this can impair the flavor of the miso.
Puree the soup using an immersion blender, or puree in batches in a blender or food processor.
To serve, garnish with chives and a sprinkle of shichimi togarashi or sesame seeds.