Wash and clean the chicken well. Dry it everywhere and sprinkle it with salt and black pepper. Drain the juice of 2 lemons and carve out their flesh. Blend them together with the medium-hard butter, soya sauce, chopped parsley, mustard and bread that's been soaked in 3 1/3 tbsp (50 ml) white wine, until the mixture cools.
Rub the chicken evenly with this paste on all sides, and put a part of it under the skin (through the neck), fill the chicken with the remaining mix and in the opening, place half of the third lemon to plug the hole. In a greased oven dish, put the cleaned potatoes and sprinkle them well with salt, black pepper and white pepper. Add another 2/5 cup (100 ml) of wine.
Distribute the chicken on top and cover the oven dish with foil. Put the lemon chicken with potatoes in a preheated 365°F (185 °C) oven, for 30-35 minutes. Then remove the foil, top the chicken with the sauce from the pan and finish baking.
Serve the chicken with slices from the third lemon.