Heat the oil and butter, then saute the onion, carrot, and celery about 5 minutes, until softened. Add the squash, apple, chicken broth, and spices and simmer until the squash is soft. I had large chunks so this took about 30 minutes but I wasn't in a hurry. It may have been done sooner and I just didn't check.
Puree the soup. I love my hand immersion blender for stuff like this. Serve with a dollop of sour cream in each bowl.