Trim the chicken breasts of any stray gristle, remove the 'tenderloins' if they are still attached to the breasts. Flatten them out slightly with the back of a skillet.

Season the breasts generously with salt and pepper. Flour them lightly.

Melt half the butter in a braising pan over medium-high heat. When the butter has melted and begins to turn color, add the chicken breasts, 'top' side down, and brown them for 5-6 minutes.

Turn the chicken breasts over. Lower the heat and add the rest of the butter, along the thyme and garlic if using. As soon as it melts, cover the pan tightly. Let the chicken breast braise undisturbed for 15 minutes.

Uncover the pan. Taste and adjust the butter sauce for seasoning, and remove the garlic and thyme if you used it. Optionally, sprinkle the lemon juice over everything.

Serve the chicken breasts right away, napping them generously with the butter.