1) Preheat oven to 400 degrees.
2) Spray a large roasting pan with olive oil. Place squash cut side down on the oiled pan, along with quartered onions and halved apples.
3) After about 20 minutes, scoop the apples off of the pan and into a blender container and turn over the onions.
4) After 10 more minutes, add the tender, caramelized onions to the blender container with the cooked apples.
5) After another 30 minutes, or after about 1 hour total, take the tender cooked squash out of the oven and scoop some squash meat into blender.
6) Add a cup of stock or soup base mixed with water to the blender. Blend until the chunks are gone, but the mixture still has texture. Add the mixture to a large sauce pan. Add the remaining squash to the pan and mix well with the blended ingredients.
7) Heat through, adding Greek yogurt and both peppers or good quality curry powder. Be careful, because more than 1/8 tsp. of white pepper can overpower this soup. Salt to taste. Top each bowl with a dollop of Greek yogurt. Enjoy all winter.