To make the bread sauce; bring the milk to the boil with the onion in it and let it infuse for approximately 20 minutes. Remove the onion and add the remaining ingredients. The sauce should be of a loose, dropping consistency. Set aside and keep warm.
To make the game chips; peel the potato and slice thinly. Remove as much starch as possible by rinsing in cold water, then pat dry. Heat the oil and deep fry for two to three minutes until golden brown.
To cook the grouse; Preheat the oven to 200°C/400°F/Gas Mark 6. Season and put the juniper berries inside the cavities of the birds. Tuck a sprig of thyme under each leg and lay two rashers of bacon over each breast.
Heat the fat in a roasting tin and sear on each side. Roast for 16 to 20 minutes, depending on size, then remove from the tray and keep warm. Add the root vegetables, any juices, stock, sloe gin and red wine and simmer gently for approximately six minutes. Sieve into a saucepan and check the seasoning.
Serve with the game chips, vegetables, bread sauce and a pot of redcurrant jelly.