In medium saucepan cook potatoes, covered, in enough boiling salted water to cover for 5 minutes or until just tender. Drain and cool. Cut corn from cob. On large serving platter arrange the potatoes and tomatoes. Sprinkle with corn and 1/4 cup basil.
For dressing, in a screw-top jar combine oil, vinegar, shallot, mustard, sugar, and salt and pepper to taste. Cover and shake well. Pour dressing over potato mixture.* Sprinkle salad with feta cheese and basil leaves. Makes 8 to 10 servings.
If desired, cover and chill salad up to 4 hours. Let come to room temperature before serving. Sprinkle with feta cheese before serving and garnish with basil leaves.
Refrigerate salad up to 4 hours. Sprinkle with feta cheese and basil leaves, and let come to room temperature before serving.