Place the chicken breasts, corncobs and the fresh thyme in a Dutch oven. Cover with the chicken stock and 1 cup of water. Bring to a boil, lower the heat and simmer, covered, for 15 minutes or until the chicken is cooked through. The chicken is done when it feels firm to the touch and a meat thermometer inserted in the center reaches 170°F. Transfer the chicken to a cutting board. Discard the corn cobs. Pour the chicken stock into a bowl or a large measuring cup, adding enough water to make 4 cups, if needed. When it’s cool enough to handle, shred the chicken into bite-sized pieces.