Preheat oven to 400 degrees F. Peel squash and scoop out seeds. Cut squash into 1-inch to 2-inch cubes.

Place cut squash on two large baking sheets. Drizzle with 1½ tablespoons olive oil each, season with salt and pepper. Roast in oven for 15 minutes. Use a spatula to flip squash, rotate pans and place back in the oven for 15 more minutes, or until squash is cooked through and starts to caramelize.

While squash is cooking, prepare onion, celery, garlic and sage.

Heat remaining olive oil in a large pot over medium heat. Once heated, add onion and cook until onions just begin to caramelize (about 20 minutes). Add celery and garlic, cook for 1 to 2 minutes, then add in 2 cups vegetable broth. Bring to a simmer.

Once mixture is simmering, add in roasted squash, sage and coconut milk. Bring back to a simmer and cook for about 5 minutes.

Use an immersion blender to purée until smooth. For a thinner soup, add additional 1 cup vegetable broth. Taste and adjust salt and pepper, as needed.

Serve with chopped chives as garnish (optional).