In large frying pan over medium heat, bring stock to boil. Add chicken. Cover and cook until tender, about 15 minutes. Remove from pan and let cool 5 minutes. Shred or cut meat into bite-size pieces. In large bowl, combine chicken, tomatoes and mangoes. In small bowl, whisk together oil and lemon juice.
Pour over chicken and toss to combine. In small bowl, combine yogurt, mayonnaise and ginger. Divide Swiss chard among salad plates. Top with chicken. Serve yogurt dressing on the side.