Place chicken breasts between two sheets of plastic wrap or in a large Ziploc bag and pound evenly until approximately 1/2-inch thick.
Once flattened, season both sides with salt and ground black pepper.
Heat the olive oil in a large skillet over medium-high heat. Once the oil is hot, cook the chicken until golden-brown, approx. 3-5 minutes per side. Remove and set aside.
Melt butter in the skillet and sprinkle in flour. Let flour bubble in the butter for 1-2 minutes.
Whisk in chicken stock until sauce thickens and is smooth.
Mix in juice of 1 lemon and stir in capers. Sauce should be a little thick.
Return chicken breasts and any escaped juices to sauce and simmer for 8-10 minutes, or until the chicken is cooked through. Slice remaining lemon into wheels and lay over chicken and sauce.
Garnish with chopped parsley.
Garnish with lemon slices and chopped parsley, if desired.