Drain Mandarin oranges and reserve juice. In a large bowl, combine salad greens and fruit. Set aside.
To make the dressing, in a small saucepan over medium-low heat, combine vinegar, 1/3 cup reserved Mandarin juice, salt, and sugar. Gently heat until sugar is dissolved. Remove from heat. Stir in white chocolate until melted. Set aside to cool. Do not refrigerate, as white chocolate will set.
Before serving, slowly whisk in olive oil. Spoon desired amount over salad and toss. Serve remaining dressing on side.