Have the dressing ingredients ready to go, so the hot beans can absorb the sauce and maximize the flavor of the dish!
Bring a stockpot of water to a boil.
In the meantime, make the dressing by combining mustard, vinegar, olive oil, garlic, capers, and shallot in a jar with a tight-fitting lid. Shake well to combine.
When water is at a rolling boil, add beans and cook for 5 minutes.
Drain cooked beans and toss with chopped parsley and add dressing, tossing to cover hot beans. Serve warm.