Cut the chicken breasts in half horizontally. Put each piece between two sheets of plastic wrap and pound them to 3/8 inch thick.

Add the chicken stock, lemon juice, and capers to the pan. Using a wooden spatula scrape up the browned bits. Add any accumulated juices from the reserved plate of chicken to the pan, then precede to reduce the sauce by half.

Remove pan(s) from heat and whisk in the cold butter and parsley. Return chicken to pan and turn to coat with sauce. Serve on a platter family style or plate.