Combine water and half of the coconut milk in a pot over medium heat. Add the galangal, lemongrass, and kaffir lime leaves. Bring the mixture to a boil, then reduce the heat and let it simmer gently.

Add the onion, carrot, mushrooms, vegetarian bouillon, salt, and tamarind paste. Stir well to combine. Let the soup simmer until the vegetables are tender. Add the tomatoes near the end and let them soften slightly.

Stir in the remaining coconut milk, then turn off the heat. Add the chilies, cilantro, and green onions. Serve warm and enjoy!