Preheat the oven to 425°F. Line a pan with aluminum foil. Put the whole squash onto the pan. Poke it in several places with a sharp knife. Roast until a skewer or paring knife goes in easily, 60-80 minutes. Or, cook the squash in any way you’d like until soft.
Once the squash is cooked, heat the butter in a large saucepan over medium heat. Add the onion and sauté until softened, 2-3 minutes.
Put the squash, sauteed onion, basil leaves, coconut milk, maple syrup, salt&rest of spices into a heavy-duty blender or a food processor. Puree until smooth. (Alternately, you can use an immersion blender to puree it all in the saucepan).
Transfer the mixture back to the sauce pan. If you’d like the soup thinner, stir in vegetable stock to achieve the desired consistency. Heat the soup over medium, stirring occasionally, until steamy and hot but not boiling.
Remove from heat. Add the lemon juice. Stir.
Taste. Add more salt and maple syrup if desired.
