Add the carcass, skin, & drippings from the roasted chicken to a large pot or dutch oven, fill it with water, bring to a boil, then turn the heat down and simmer for 1 hour for low histamine broth.
Heat butter or olive oil in a large pot over medium heat, then add chopped veggies, split peas, herbs, and spices. Let everything “sweat” over medium heat for 15-20 minutes.