Preheat the oven to 230°C.
To prepare the birds, place them in a roasting tin and spread a thin layer of butter over the skin. Lay the rashers of bacon on top and season with black pepper. Place in the oven and roast for 10mins.
Meanwhile prepare the gravy by putting the neck, giblets, bay leaf, celery, onion, carrot and herbs into a saucepan, along with the stock and herbs. Bring to the boil and simmer for 10mins. Skim the fat off the top, remove the neck and giblets, and stir in the redcurrant jelly. Check the seasoning.
Remove the bacon from the birds and bake for another 20mins.
Quarter the apples and cut into thin slices. In a frying pan melt the butter and add in the apples. Cook over a low heat for 5mins or until the apple is tender.
Add the sugar, stirring until it completely dissolves and starts to caramelise. Add in the Calvados, and make sure that the apple slices are well-coated in the caramelised syrup.
Remove the birds from the oven and allow to rest while you make the game chips. Heat the oil in a large saucepan.
Using a potato peeler, peel off long ribbons of parsnip and add them to the hot oil. Deep-fry for approx 30 seconds until golden and crispy. Carefully remove the chips from the oil with a slotted spoon and drain on kitchen roll. Sprinkle with a little sea salt.
Serve the grouse whole or jointed, with piping-hot gravy, game chips and caramelised apples.