Chicken sauteed with apples and onions

This will make a great fall meal, but I couldn't wait. I love apples. This would also be fabulous with Granny Smiths and fennel. 4 boneless, skinless chicken breasts. If they are big, use 2 and butterfly them into cutlets. 1 tablespoon EVOO 1 firm apple, I used a braeburn, sliced into 1/4 inch slices (see note) 1 cup apple juice (I use Martinelli all natural) 1 large onion, halved and thinly sliced 1 clove garlic, minced fine 1 teaspoon fresh thyme leaves sea salt and pepper 2 teaspoons dijon mustard ( I use a very grainy one) Pound chicken breasts between two sheets of parchment until about 3/4 inch thick. Lightly salt and pepper. Heat a large saucepan over medium high heat. When hot, add oil. Saute the chicken until golden, around 3 minutes on each side. Add remaining ingredients except for mustard. Simmer, covered, until chicken is tender and onions are cooked. Remove chicken, apple and onion from the pan. Whisk in mustard. Boil sauce for 5 minutes until thickened. Pour over chicken. I served with brown rice and a tossed salad.