Preheat oven to 350 degrees. Cut butternut squash in half and remove seeds. Place cut side down in a 9x13 casserole dish. Fill with ~1/2 C water and bake for 45 min-1 hr until very soft. Set aside.
Dice leeks and onions. Melt butter in a large pot over medium heat. Cook leeks and onions until soft, about five minutes.
Peel and dice sweet potato, carrots, and apple. Add to pot with chicken broth. Bring to a boil, cover and reduce heat to low and simmer until vegetables are very soft and easily pierced with a fork.
Add cooked butternut squash and simmer about 5 minutes longer until squash is warm.
Using a stick blender, puree the soup right in the pot. I like the soup very very smooth so I try to get all the chunks out.
Once the soup is pureed to your liking, add 1/2 C cream or milk and 1/4 C apple juice. I used cream, but the soup is very rich and creamy on it's own so it wouldn't hurt to use milk instead.
Add cinnamon, and salt and pepper to taste.
Garnish with cream, green onions/chives, or pumpkin/sunflower seeds. Serve with crusty bread and a side salad or as a side for a harvest dinner.