Combine all ingredients (except for cilantro and yogurt) in a slow cooker.
Heat on low for 6-8 hours, or high for 3-4 hours, until squash is very tender.
Use an immersion blender to blend the soup to a smooth consistency. (alternatively, you can use a regular blender in batches to process the soup). If soup is too thick, add some more chicken stock or some water.
Garnish with cilantro and Greek yogurt (optional)
If soup is too thin, which is unlikely unless you use a small butternut squash, leave cover off of slow cooker and continue cooking on high for a while until it's thickened (or transfer it to a pot on your stove to simmer uncovered for a faster option).
To prep ahead: Peel and chop all the vegetables and add them along with the the spices to the slow cooker ahead of time. Keep in the fridge for up to a week or the freezer for up to six months until you are ready to cook (at which point, add vegetable stock and coconut milk)
Freezer directions: You can store any leftovers in an airtight container in the freezer for up to six months.
You can make this soup on the stovetop as well. Just sauté the vegetables in a bit of olive oil over medium-high heat until softened. Add the spices, stir to combine, and then add vegetable stock and coconut milk. Simmer on low for approximately 30 minutes, or until squash is tender. Blend as instructed above.
The provided nutrition information does not include any added sodium from seasoning to taste, any optional ingredients, and it does not take brands into account. Feel free to calculate it yourself using this calculator or by adding the recipe to Yummly.