In a covered saucepan, cook potatoes in boiling water for 20 to 25 minutes or until just tender; drain. Peel and cut potatoes into 1/2-inch cubes.
In a very large bowl, combine potatoes, bacon, cheese and scallions.
Combine mayonnaise, cream, mustard and pepper. Add to potatoes. Toss to coat. Cover and chill for 6 to 24 hours. Makes 12 side-dish servings.