1. In a 2-quart slow-cooker add prunes and cover them with water.
2. Cover pot with its lid.
3. Stew the prunes on HIGH for almost 1 1/2 hours or on LOW for about 3 hours.
4. Once the prunes are soft turn them into a large bowl
5. Stir the Cointreau, sugar and orange juice into the warm prune mixture.
6. Fold in the mandarin segments
7. Cover the bowl with plastic wrap and refrigerate until chilled.
8. Spoon the prune mixture into individual dessert bowls.