Mix first 3 ingredients in medium bowl to blend. Fold in 1/4 cup
caviar. Cover and refrigerate. (Dressing can be prepared 2 hours
ahead. Keep refrigerated.)
Cook potatoes in large pot of boiling salted water until tender,
about 20 minutes. Using slotted spoon, transfer potatoes to work
surface to cool. Cook beans in same pot of boiling salted water until
crisp-tender, about 5 minutes. Drain. Rinse beans under cold water to
cool. Cut beans into 1" lengths. Cut potatoes into quarters.
Combine potatoes, beans, endive, chopped eggs, and green onions in
large bowl. Add dressing and toss gently to coat. Season generously
with salt and pepper. Divide salad among 4 plates. Top each with 1 ts
caviar.