1. Sauté leek in coconut oil for 3 minutes.
2. Add squash, broth, milk, apple, garlic, sage, and cinnamon. Bring to a boil then reduce heat and simmer for 30 minutes.
3. Add vinegar, salt and pepper. Purée until smooth, adding water if too thick.
4. Top each serving with ¼ cup chopped walnuts.