In a large dutch oven or heavy bottomed pot, heat butter over medium heat. Place chicken breasts, skin side down in pot and lightly brown (2-3 minutes)
Turn chicken breasts over (bone side down), add onions, celery and peppers. Saute until soft, 2-3 minutes.
Add water bring to a simmer. Cover and turn heat to low and cook for 1 hour.
Remove chicken breasts from liquid, allow to cool enough to handle.
Remove skin and bones (discard or freeze use in bone broth next time you make it) Roughly chop or shred chicken meat and add back into soup.
In a small bowl or cup, whisk together potato starch and about 1/4 cup of the liquid from the soup until smooth. Add into the soup and stir well to combine.
Allow thickener to cook in soup for 2-3 minutes then turn off heat and stir in coconut milk.
Serve in bowls topped with chunks of avocado. It is also delicious served overtop of rice.
Notes
You can add 1 cup of frozen corn and/or a can of white beans, if desired.