Preparation Set a steamer basket in a large pot filled with about 1" water. Cover pot and bring water to a boil over high heat. Place potatoes, leeks, then eggs in steamer basket, cover, and steam 10 minutes. Using tongs, transfer eggs to a bowl of cold water. Meanwhile, whisk oil, vinegar, honey, cayenne (if using), and 1 tsp. salt in a small bowl. Stir in parsley and capers; set aside. Add broccolini to steamer basket on top of potatoes and leeks; season with remaining 1/2 tsp. salt. Cover and steam until broccolini is tender, 3–5 minutes. Meanwhile, peel eggs and break or cut in half. Swoosh a bit of mayonnaise in wide shallow bowls or on plates. Divide potatoes, leeks, broccolini, and eggs among bowls or plates. Drizzle with reserved dressing.