This is a great fall soup. I like it for a lunch or a light dinner with some crusty bread. It's easy to make vegetarian by using vegetable broth rather than chicken. Personally, I like the richness the chicken broth gives it. You could use sour cream instead of yogurt if you like. You could even prep the recipe, let the veggies cook down in the slow cooker and puree when you are ready to eat. You can find the original recipe here.
Preheat oven to 350 degrees F (175 degrees C). Line a baking sheet with parchment paper or aluminum foil.
Place squash halves and onion onto the prepared baking sheet. Wrap garlic in foil and set with other vegetables.
Roast in the center of the oven for 45 to 60 minutes, until the squash is tender. Remove from oven and set aside until cool enough to handle.
Squeeze garlic cloves out of their skin like paste into a food processor. Scrape the flesh from the squash and place into the food processor along with the roasted onion. Puree until smooth. Add vegetable broth if necessary. Transfer the pureed mixture to a stockpot and stir in vegetable broth. Season with the bay leaf, brown sugar, curry powder, oregano, cinnamon, nutmeg and salt and pepper to taste. Bring to a boil and simmer gently for 10 minutes. Remove from heat and stir in yogurt.
Remove bay leaf and serve hot. Garnish with fresh parsley if desired.