Creamy Butternut Squash and Apple Soup

Heat oven to 400 degrees. Slice the squash in half, and scoop out seeds. Place cut side up in a baking dish, and cover tightly with foil. Bake until the squash flesh is soft when pierced with a knife, about 45 minutes.
While the squash bakes, heat the oil in a pot over medium-high heat. Add the leeks, and cook until softened, about 8 minutes. Add the apples and vegetable broth, and bring to a simmer. Cook until the apples are soft, about 12 minutes.
Scrape the flesh of the baked butternut squash into the pot with a spoon. Off heat, add the milk. Using an immersion blender, puree the soup until creamy. (Alternatively, transfer the soup in batches to a blender or food processor, and puree.) Add the salt, and re-warm over low heat if needed.
Ladle soup into bowls, topping with a dollop of yogurt and a sprinkle of chives.