Put the stock, onion, carrots, butternut squash, apple, nutmeg, cinnamon, sage, salt, pepper and bay leaves in a large Crock Pot.
Allow the soup to cook on high for 3-4 hours or low 6-8 hours until all the vegetables are completely tender.
Remove the bay leaves.
With an immersion blender, blend the soup well. Alternatively, you can blend the soup in a standard blender in batches. If it's too thick add more broth.
Stir in the Greek yogurt!
Serve with a dollop of greek yogurt and pumpkin seeds!