1 1/2 teaspoons olive oil
3 cups chopped onions
2/3 cup chopped carrots
1/2 cup chopped celery
1 3/4 pounds butternut squash, peeled, seeded, diced (about 4 cups)
3 garlic cloves, minced
4 cups water
1 tablespoon chopped fresh oregano
1 Granny Smith apple, peeled, cored, diced (about 1cup)
1 tablespoon curry powder
1 teaspoon chopped fresh dill
plain yogurt
fresh dill sprigs (optional)

Heat 1 teaspoon olive oil in large pot over medium heat. Add 2 cups onions, carrots and celery; sauté until onions are translucent, about 10 minutes. Add 4 cups water and oregano. Cover and simmer until vegetables are soft, about 15 minutes.

Meanwhile, heat remaining 1/2 teaspoon oil in heavy medium nonstick skillet over medium high heat. Add remaining 1 cup onions and cook until golden, about 5 minutes; add curry and cook 1 minute. Remove from heat. Mix in chopped dill. Set curried onion-apple mixture aside.

Working in batches, puree soup in blender. Return soup to pot; mix in curried onion-apple mixture. Bring to simmer. Season to taste with salt and pepper.  Dollop each serving with dollop of yogurt and fresh sprig of dill, if desired.

Note: Soup can be made 1 day ahead. Cover and refrigerate.