Combine potatoes, breadcrumbs, peanuts, butter, onion juice, and sage in a medium-size mixing bowl; add 1/2 teaspoon salt and pepper. Stir dressing until well combined. Set aside.
Remove giblets and neck from goose; reserve for other uses. Prick fatty areas of goose with a fork at intervals. (Do not prick breast. ) Stuff dressing into cavity of goose, and close cavity with skewers; truss. Sprinkle remaining salt over surface of goose. Lift wingtips up and over back, tucking under bird securely. Fold neck skin under and place goose, breast side up, in a shallow roasting pan. Bake at 375° for 2 to 2 1/2 hours until drumsticks and thighs are easy to move. Baste goose frequently with additional melted butter.