Add the Penne to the boiling water and cook until not quite tender, about 8 minutes. When the Penne has cooked for 8 minutes, stir in the Swiss chard and cook until the pasta and chard are tender, about 3 minutes more. Drain well and transfer to a serving bowl. Toss the pasta and Swiss chard with the garlic mixture and season with salt and pepper. Serve sprinkled with the bread crumbs.
Juniper berries lend a pungent note to the stuffing.
Melt the butter in a shallow roasting pan large enough to hold the birds without touching. Remove the giblets from the birds and reserve 2 of the livers. Rinse the game hens inside and out and pat dry with paper towels. Trim the membrane from the livers and quarter them. Process the bread, parsley, juniper berries and prosciutto with the metal blade of a food processor until coarsely chopped, about 10 pulses.