First make the potatoes, mash them and let them dry well. Beat the egg whites very stiffly but not dry. Mix the egg yolk and capers and cream into the mash and fold in the egg whites. Form small cakes and fry in the butter until brown.
Preheat the oven to 425 degrees F.
Spread each woodcock generously with butter and cover with a bacon rasher. Roast in the oven for 10 to 15 minutes, depending on how you like them, more if you must.
For the sauce, saute the livers in butter until just cooked, mash and press them through a fine sieve. Put the puree in a pan, thin with white wine and stock, add juniper berries, seasoning and lemon juice, and simmer for a few minutes.
Place the cooked woodcock on the potato cakes and serve with the sauce.