"Creamy soup with mild spice and a zip of citrus. It is inspired by Tom Kha Gai from Laotian and Thai cuisines, but it comes together quickly from ingredients that are easily and routinely available--real Tom Kha needs fresh lemon grass, kaffir lime leaves, and galangal root, which are not always available in my locale."
Warm coconut milk in a saucepan over medium heat, about 5 minutes. Whisk in green curry paste, lime juice, salt, pepper, hot sauce, and cumin. Stir in chicken, mushrooms, and white part of the green onion. Simmer soup until flavors combine, 5 to 10 minutes.
Ladle soup into bowls and garnish with remaining green onion.