Preheat the oven to 425 degrees
Cut the squash in half lengthwise. Remove the seeds, brush with olive oil and sprinkle with salt and pepper
Roast the squash until it's soft and a bit brown - about 45 minutes
Let the squash cool a bit and scoop all that lovely, silky flesh out with a spoon (you can do this ahead of time and refrigerate the squash until you're ready to make the soup)
Grab your lemongrass, cut the ends off and give it a smash with a hammer or large pan - good way to deal with any unresolved issues!
Sauté the chopped onion in a tablespoon of olive oil until soft and translucent - about 5 minutes
Add the garlic and sauté for another 30 seconds
Add the cooked squash and enough broth to cover it by about an inch - likely between 2 and 3 cups
Add the lemongrass stalk, bring to a boil, reduce the heat and simmer for 20 minutes
Grab some coconut milk. My favorite is Arroy-D (found at my local Asian market). They even have super cute, tiny (5oz) cans that are perfect for this soup
Remove the lemongrass and grab your handy dandy immersion blender (or throw the whole lot into a blender) and whiz away
Blend until the soup is as smooth as you like. (I like it to have a bit of texture) and add the coconut milk
Simmer for another 10 minutes or so, taste and adjust the seasonings - it's likely to need some salt
Serve with a generous helping of cilantro (unless, of course, it tastes like soap to you) and enjoy!