Place the ice cream in 4 sundae dishes and place in the freezer. Combine all the sauce ingredients (except the peach liqueur) in a saucepan and bring to a boil. Cook rapidly for about 3 minutes. Top ice cream with 2 peach halves and spoon Ginger-Walnut Sauce over each sundae. Spoon on 1 Tbls. of Southern Comfort over peach halves and sprinkle with a little chopped candied ginger, if desired.