Preheat the oven to 180C/350F/Gas 4. Rub the chicken with the butter (or oil) and season with salt and pepper.
Place the bacon rashers over the breast (if using). Place the chicken in a roasting tin and roast for 1–1¼hours. The chicken is cooked if the juices run clear when you insert a skewer between the thigh and breast.
About halfway through the cooking time for the chicken, make the sauce. Drain the soaked mushrooms through a sieve lined with muslin (or other clean fine-meshed cloth) to remove any sand or grit. Set the liquid aside.
Wash the mushrooms carefully and cut them into bite-sized pieces.
Melt the butter in a pan and add the flour, stirring it well for about a minute. Gradually add the wine, stirring all the time and taking care not to let the sauce burn.
Add the mushroom liquid to the sauce very slowly so that it doesn’t curdle, then add the mushrooms and cook for about 20 minutes.
Add the double cream to the sauce and heat through gently. Season, to taste, with salt and freshly ground black pepper.
Carve the chicken and place it on a serving platter. Pour over the juices from the roasting pan and serve with the morel sauce.