Bring the broth to a boil in a medium saucepan, add the chicken and simmer covered until the chicken is completely done. Remove the chicken from the heat and let it cool. Cut into 1/4-inch dice. In a large bowl, combine the yogurt, mayonnaise, curry powder, salt and pepper. Add the chicken to the bowl, stir until the chicken is well coated with the sauce. Fold in the almonds, grapes, and cilantro. In a large bowl, toss the greens with the lemon juice and olive oil. Arrange on individual plates, top with a scoop of the chicken salad and sprinkle with extra-virgin olive oil if desired.