of apple. Place in shallow, ungreased baking pan. Mix sugar and cinnamon together in small saucepan; add water, lemon and orange slices, and bring to a boil. Boil 7 mins. or until syrup is thickened. Discard lemon and orange slices. Pour this syrup over the apples, and bake for 30 minutes or until fork tender. Baste apples frequently during baking with syrup from the pan. They should be nicely glazed when done. To serve warm, let apples stand 10-15 minutes before continuing. Also good served cold. Place apple in glass dessert bowl, opening the apple sectionsso they spread (like flower petals) to fit the bowl. Cut sections deeper if needed to open it more easily. Fill center of apple with scoop of ice cream. Drizzle the chocolate liqueur sauce over all, and garnish with chopped walnuts. Serve immediately. CHOCOLATE LIQUER SAUCE: Melt butter and chocolate in saucepan over low heat. Add sugar and water. Cook until sauce is thickened a bit, stirring frequently. Add liqueur and remove from heat. Cool.