Grate the rind from the lemon on the finest part of the grater; keep aside. Squeeze the juice from half of the lemon, dip the chicken breasts in it and keep the rest for later. Season with salt and freshly ground pepper. Melt a little butter in a sauté pan which is wide enough to take the breasts in a single layer. Toss the breasts in butter, cover with a butter wrapper and lid and cook gently on top or in a moderate oven, 180°C/350°F/regulo 4, for 10 minutes approx. (depending on the size of the breasts). Be careful not to overcook them or they will be dry.
Remove the breasts to a warm dish, de-glaze the pan with the stock and stir to dissolve any little crusty bits remaining. Add the cream and reduce, taste and season if necessary. Add a little lemon rind, a squeeze of lemon juice and the chopped parsley, then taste again. Spoon the sauce over the chicken breasts and serve immediately with Tomato Fondue and a good green salad.