Butterfly and roast the chicken in white white and dab butter on the tops on the breasts (under the skin). Roast for 1 hour in the oven on 350.
Remove and drain the drippings into a sauce pan. Wisk in garlic, dijon, capers and lemon juice. Mix cornstarch with a small amount of water and mix in, allow to boil and thicken slightly (it won't be very thick, but it will coat this way). Salt to taste. Cut up the chicken and pour over. Garnish with lemon wedges and parsley if desired.