Preheat the oven to 400F/200C. Cut the acorn squash in half and remove the seeds but don’t throw them away, put them in a colander and rinse them. Place the acorn squash on a baking tray lined with baking paper, skin facing up. Put the seeds on the tray too, sprinkle a bit of salt and bake until squash is tender, about 15 minutes. The seeds will toast in 10 minutes.
In a medium pot melt the ghee or coconut oil over medium-low heat. Stir in the onion, celery, carrots and spices and saute for 5 minutes. Add 6 cups water, fish sauce and a pinch of salt and bring to a boil. Boil for 5 minutes then lower heat to simmer and cook until the acorn squash is ready.
Let the squash to cool for a few minutes, then using a spoon scoop the its meat into the soup. You can also peel it and then adding it to the soup.
Remove the star anise and pour in the coconut milk. Using a hand blender blitz the soup until it's partly chunky but mostly smooth.
Add the baby spinach and cook on medium heat for 3 minutes then remove from the heat.
Serve immediately with a few drops lime juice and the toasted seeds or store in the fridge up to 3 days.