strawberry rhubarb sauce for duck

2 cups duck stock (simmer neck, gizzards, half an onion and a stalk of celery while the duck is cooking)
1/4 cup white port or brandy
1 cup strawberries cut in half (or quarters if large)
1 cup cooked rhubarb with minimal sweetening
grated rind and juice of one lemon
1/4 cup cut up mint leaves

Combine stock, port, strawberries and rhubarb, bring to a boil, and simmer until strawberries are soft.  Stir in lemon rind and juice, then remove from the heat and stir in mint leaves.  Serve over roast duck.