Potato and Zucchini Salad

Name: Potato and Zucchini Salad
Ingredients: 2 lbs red-skinned potatoes, cut into 1 pieces; Kosher salt; 1 large egg yolk; 1 /4 cup apple cider vinegar; 1 1/2 tablespoons whole grain Dijon mustard; 1 /4 cup plus 1 tablespoon olive oil; Freshly ground black pepper; 1 shallot, thinly sliced; 1 Fresno chile or red jalapeño, with seeds, thinly sliced into rounds; 2 summer squash (such as zucchini or yellow crookneck squash; about 1 lb.), cut into 1 pieces; 1 cup scallion, thinly sliced; 1 /2 torn fresh basil leaves