Melt the butter in a heavy skillet, and when it is foaming and bubbling sauté the onions until just translucent.
Add the bread-crumbs and toss well with the onion, salt, sage, and pepper. If additional melted butter is needed you may add it at this time.
Add the applejack and parsley and taste for seasoning.
Stuff the birds lightly and sew up the cavity or slip several thicknesses of foil over the stuffing. Tie the legs together and slip the wings under the back.
Place the ducks on a rack in a roasting pan and rub them with salt. Roast 30 minutes at 425°F. Remove from the oven, prick the skin with a fork, and continue roasting at 325°F for 1-1/2 to 2 hours, or until the skin is nicely browned and crisp.