Warm New Potato Salad with Grainy Mustard & Herbs

1 lb small potatoes 1 1/2 teaspoons salt 3 tablespoons finely chopped shallots (about 2) 1/2 tablespoon Dijon mustard 1 tablespoon whole-grain mustard 1 tablespoon white-wine vinegar, or to taste 1/2 teaspoon black pepper 3 tablespoons olive oil 2 tablespoons Read on!