in a medium pan cook potatoes, covered, in enough boiling salted water to cover about five minutes or just until tender. Drain and cool. A large serving platter arrange potatoes and tomatoes. Sprinkle with corn and the 1/4 cup basil.
For dressing, in a screw top jar mix oil, vinegar, shallots, mustard, sugar, salt, and pepper. Cover and shake well. Pour dressing over potato mixture. Sprinkle salad with cheese and basil leaves. Makes 8 to 10 servings.