Set aside 4 small sprigs of heather for decoration, and crush the rest with a rolling pin to bruise and release flavors. Pour the whisky over the heather on a plate and leave to soak.
Crush 1/2 of the pint of raspberries and put them inside the pheasants. Spread the birds with softened butter and sprinkle with salt and pepper. Wrap them in bacon, securing the whisky-soaked heather inside. Tie the birds with string and set them in a small roasting pan. Pour over any whisky from the heather.
Roast the birds in the oven, basting them often and turning them from time to time so they brown evenly, 35 to 45 minutes. When done they should be well browned and the legs will wiggle when pulled.
Tip raspberries from the birds into the pan. Transfer bird to a carving board and cover with foil to keep warm.
For gravy: stir flour into the pan juices and cook, stirring, 1 to 2 minutes until browned. Add stock and bring the gravy to a boil, stirring to dissolve pan juices. Simmer it 2 minutes or until concentrated, then strain into a small pan.
Whisk in red currant jelly and heat until melted. Stir in remaining raspberries and cook 1 to 2 minutes until just soft. Taste gravy and adjust the seasoning. Using poultry shears, discard string from the pheasants and cut them in half, discarding backbone. Arrange them overlapping on a serving dish or on individual plates. Spoon over the raspberries with a little gravy, serving the rest separately. Decorate the pheasants with heather sprigs.