Cut 8 slices, about 5 mm (¼ inch) thick from the whole lemon. Cut the chicken up into 4 pieces, following the natural curves of bone. Cut away the wing tips. Rinse the pieces and pat dry. Squeeze the lemon half and anything left from the whole lemon into your baking dish and add the chicken pieces, garlic, olive oil, bay leaves and thyme. Add salt and pepper and turn the chicken pieces to coat them well. Leave, skin side up, for 1 hour or so to marinate.
Preheat the oven to 200°C (400°F/Gas 6). Tuck the lemon slices under the chicken with the garlic and thyme. It’s good if they see some open air so they get caramelly golden, but not too much or they will burn and become bitter. If you see them burning during roasting, tuck them completely under the chicken. Roast for 30 minutes, then pour 125 ml (4 fl oz/½ cup) of the water around the edges. Roast for another 20-30 minutes, until the skin on top is lovely and crisp and the juices are deep golden and lovely. Add an extra dribble of water in this time if needed.
While the chicken is roasting prepare the salad. Rinse and dry the valeriana and put in a wide bowl ready for tossing later. Whip the oil, mustard and vinegar in a small bowl, then add the garlic and season with salt and pepper. Leave to sit and mingle.
Take the dish from the oven. Remove the chicken and lemon slices to an oval platter and cut the chicken with poultry scissors into smaller pieces. Add the cream and remaining 60 ml (2 fl oz/¼ cup) of water to the dish and put on the stovetop to bubble up and reduce, scraping up any interesting bits caught on the base with a wooden spoon. When you are satisfied with the thickness turn off the heat. Turn the salad through gently with about 2 tablespoons of the dressing — it should be just a light coat, not a dressing gown. Taste and adjust the seasoning if necessary. Divide among serving plates. Add the chicken and drizzle the sauce over. Serve with bread.