Prepare vegetables by chopping onion, mincing garlic, grating ginger, cubing butternut squash, and chopping carrots.
In a large pot, heat olive oil over medium heat. Sauté onion until soft (5-7 minutes), then add garlic and ginger for 1 minute. Stir in cumin, coriander, and cayenne pepper.
Add butternut squash and carrots to the pot; stir well to coat with spices. Pour in vegetable broth until veggies are submerged and season with salt and black pepper.
Bring to a boil, then reduce heat to low and simmer for 20-25 minutes until vegetables are tender.
Blend the soup until smooth using an immersion blender or regular blender. Stir in coconut milk if desired, then reheat gently before serving.