In a large mixing bowl combine shallot, garlic, capers, red wine vinegar, lemon juice and a pinch of salt and pepper. Stir together and allow it to sit for at least 5 minutes. Then whisk in wholegrain mustard and olive oil.
Steam the green beans for 2-3 minutes until tender crisp, but not soft. Pour the warm green beans into the mixing bowl with the vinaigrette and stir to coat. Allow them to marinate in the vinaigrette for at least 5 minutes before serving. Taste and add additional salt and pepper as needed. Serve warm or at room temperature. Or chill and refrigerate to serve later. Enjoy!