In a large sauce pan with a lid, heat the onion and olive oil, cooking the onion for about 3 minutes until translucent. Add the cauliflower, season with 1/2 teaspoon salt and continue cooking, for 1 minute. Add the water or stock, coconut milk and curry powder, stir and cover, cooking for about 5 minutes until the cauliflower is soft. Remove from heat, blend with an immersion blender, or remove to blend in a food processor or blender. (Alternatively, you could mash with a potato masher or even leave it chunky, just cut the pieces smaller in the beginning.) Stir in the cilantro, green onion and hot sauce to taste.