Mix cornstarch with water and set aside.

Heat 1 tsp (5 mL) oil in a large non-stick skillet over medium heat. Add the mushrooms, onion and garlic; cook stirring often, for 5 minutes or until softened. Remove and set aside.

Heat remaining oil in skillet, add chicken breasts, sauté until golden brown, about 5 minutes or until chicken reaches an internal temperature of 165°F (74°C). Add vegetables, chicken stock, apple cider, Calvados, thyme, rosemary and salt. Heat to boiling, reduce heat to simmer. Turn chicken pieces over several times during cooking and continue cooking 12 to 14 minutes or until the chicken is tender and juices run clear when pierced with a fork. Transfer chicken to platter, tend with foil. Increase heat to high, reduce liquid by half, about 3 to 5 minutes. Reduce heat to low and whisk in cornstarch mixture. Cook until thick and sauce is clear. Spoon over chicken breasts.