For the sauce, wipe out the saute pan with a dry paper towel. On medium heat, melt 1 tablespoon of the butter and then add the lemon juice, wine, the reserved lemon halves, ½ teaspoon salt, and ¼ teaspoon pepper. Boil over high heat until reduced in half, about 2 minutes. Off the heat, add the remaining 2 tablespoons of butter and swirl to combine. Discard the lemon halves and serve one chicken breast on each plate. Spoon on the sauce and serve with a slice of lemon and a sprinkling of fresh parsley.