American Hatch Potato Salad
1 cup mayonnaise 1 tablespoon lemon juice 1 tablespoon pickle relish 1 teaspoon kosher salt 1 teaspoon vegetable oil 2 Hatch chile peppers, halved and seeded, or … 2 peperoncini peppers, minced 2 pounds potatoes, peeled and cubed 2 ribs celery with leaves, chopped 2 tablespoons kosher salt 2 tablespoons prepared mustard ground black pepper to taste ¼ cup chopped flat-leaf parsley ½ red onion, finely chopped