- In a pot of salted boiling water, cook the green beans for about 5 minutes or until tender. Cool in an ice bath. Drain.
- On a work surface, split the beans lengthwise, if desired (see note).
- In a large bowl, combine the mayonnaise, mustard, vinegar, capers, horseradish and shallot. Add the beans. Season with salt and pepper and toss well.
Green beans split lengthwise not only look super elegant, they are also more delicate and readily absorb any dressing or sauce.