How to Make It
Prepare Pickled Onions: Toss together first 4 ingredients and 1/4 cup water in a bowl. Cover and chill 1 to 12 hours.
Prepare Vinaigrette: Whisk together cider vinegar and next 4 ingredients. Add oil in a slow steady stream, whisking constantly until smooth.
Prepare Salad: Cook beans in 6 qt. boiling salted water in a large Dutch oven over medium-high heat 3 minutes or until crisp-tender; drain. Plunge beans into ice water to stop the cooking process; drain and pat dry.
Cut hearts of palm into 1-inch-thick slices, and separate into rings. Toss haricots verts and hearts of palm with vinaigrette; add salt and pepper to taste. Arrange on a platter. Drain onions, and sprinkle over salad. Gently toss, if desired, and serve immediately.