In a medium stockpot, bring the chicken broth to a boil. Add the bay leaf and chicken, then bring back up to a boil.
Reduce the heat to medium-low and simmer covered for 15 minutes, flipping over at the halfway mark. The internal temperature should read 165º F.
Discard the bay leaves and reserve the chicken on a plate until cool enough to touch, then shred and set aside.
While the chicken is cooling, prepare the dressing in a large mixing bowl by whisking together the yogurt, mayonnaise, lime juice, salt, black pepper, cumin and garlic powder.
Add the avocado, red onion, cilantro, and cooled chicken to the bowl. Gently toss all of the ingredients together.