Heat the oil in a large pan over medium heat; add onion and cook until softened, but not brown, about three minutes.
Stir in chili powder and tomato paste. Add chicken to tomato-chili mixture and stir to coat entirely.
Add about ½ of the chicken stock and bring mixture to a simmer. Cover and cook for 20 minutes.
Add tomato, corn, black beans and remaining chicken stock to the pan. Bring mixture to a simmer and cook for an additional five minutes then remove from heat. Top with avocado, cilantro, lime, and yogurt, if desired.
Photography and styling by Julia Gartland