Step 1Place cider in small, heavy saucepan. Add sugar. Use your finger to stir sugar into cider.
Step 2Heat over medium-high heat until boiling and sugar dissolves, stirring 1 to 2 times. Cook, without stirring, until dark amber (like an old penny), about 4 to 5 minutes. If syrup colors unevenly, gently swirl pan to mix.
Step 3Remove from heat. Stir in walnuts.
Step 4Use fork to lift nuts out of syrup and place on baking sheet lined with buttered parchment paper or foil. If syrup becomes too thick or hard to transfer nuts as indicated, gently reheat syrup over low heat until nuts can be removed easily. Repeat this process as needed.
Step 5Cool completely. Place in airtight tin and freeze until serving time. (Can be frozen up to 1 month.)
Step 1Heat cider in large skillet over high heat until boiling. Cook, uncovered, until reduced to 1/2 cup, about 20 minutes.
Step 2Cool completely; refrigerate overnight and up to 1 week. Let come to room temperature before using.
Step 1Place scoops of ice cream in small sundae dishes. Spoon sauce over, dividing evenly. Sprinkle with candied walnuts. Serve immediately.