Place 25g/1oz of butter inside each pheasant. Season generously with salt and freshly ground black pepper. Place a rasher of bacon and a bay leaf on each bird.
Put the onion, mushrooms, carrot, leek, garlic cloves and thyme in a roasting tin and place the birds on top.
Spread more butter over the birds and roast in the oven for about 45 minutes.
Meanwhile, heat the oil in a large heavy-based frying pan over a medium heat. Add the bacon lardons and fry until crisp. Remove with a slotted spoon.
Add the leek and celeriac and cook for 6-8 minutes. Return the bacon to the pan. Addthe cider and continue to cook until the volume of the liquid has reduced by half. Add the stock and reduce by half again.
Stir in the cream and thyme leaves. Season to taste with freshly ground black pepper.
To serve, carve the pheasants and place onto serving plates. Spoon the roasted vegetables alongside and spoon over the bacon and celeriac.