American Picnic Potato Salad from The Silver Palate Cookbook by Julee Rosso and Sheila Lukins

Ingredients

• 5 tablespoons Dijon or herb mustard (dill, tarragon, or basil)
• 4 pounds boiling potatoes, peeled
• Salt, to taste
• ½ cup white wine vinegar
• 20 hard-cooked eggs, peeled and quartered
• ½ cup olive oil
• ¼ teaspoon Freshly ground black pepper
• 1 cup thinly sliced red onions
• 3 medium-size cucumbers, peeled, seeded, and sliced
• 1 cup celery strips, 1 inch long, ¼ inch wide
• 2 cups mayonnaise (preferably Hellmann’s), plus more if needed
• 1 cup chopped fresh Italian (flat-leaf) parsley