Place the chicken carcass, water, onion, celery, and parsley stems in a large stockpot. Bring to a boil over high heat, then reduce heat to medium and simmer for 1 hour. Strain the mixture, reserving the liquid. Separate any chicken meat from the carcass and reserve. Discard remaining solids.

Heat coconut oil in a large pot over medium-high heat. Add the white and light green parts of the green onions and ginger. Cook until fragrant, about 1 minute.

Sprinkle with salt and stir. Add mushrooms and cook until lightly browned, about 3 minutes.

Add carrots and the remaining salt, cooking for 3 minutes while stirring. Add pepper, garlic powder, and 6 cups of reserved broth.

Stir and scrape up any browned bits from the pot. Add coconut milk and reserved chicken pieces. Bring to a simmer and cook for 10 minutes.