I must confess that pheasant is probably my least favourite of the game birds. It has a tendency to dry out in the oven before you know it and can be very disappointing. It must either be timed to perfection or slow cooked. Using pheasant in a soup like this, however, gets around the problem - and one bird goes a long way. You can prepare the soup base, roast the chestnuts and get everything together the day before, ready to reheat and assemble everything just before serving.