1 butternut squash, halved and seeded
2 large onions, peeled and quartered
1 medium head garlic
6 cups vegetable broth
1 bay leaf
1 teaspoon brown sugar
1 teaspoon mild curry powder
1/2 teaspoon dried oregano
1/2 teaspoon ground cinnamon
1/4 teaspoon ground nutmeg
salt and pepper to taste
1 cup plain yogurt
1/4 cup chopped fresh parsley (optional)