Place the shallot, vinegar, mustard, salt, and pepper in a medium-size mixing bowl. Whisk to combine, and let sit for 5 minutes to mellow out the shallot.
Whisk the olive oil in with a slow, steady stream. Continue whisking until the oil is emulsified with the vinegar or citrus. Taste and adjust seasoning. Is the oil/vinegar ratio balanced? Is there enough salt?
Serve as a dressing for cold and warm salads, grain bowls, roasted vegetables, or as a marinade for grilling.
Notes
Notes: Recipe may be doubled or tripled. Refrigerate, tightly sealed, for up to 7 days.
Recipe by The Gardener Cook at https://www.thegardenercook.com/french-mustard-vinaigrette/