Celery paired with a mustard-mayonnaise dressing is a French favorite, best epitomized by the classic dish, celeri en remoulade.
Although that recipe calls for celery root (or celeriac), not celery, we've taken that concept and given it a twist with this American-style slaw. For a more colorful slaw, add 1 cup of shredded carrots and/or red cabbage.
Wash the celery well and pluck all the leaves. Slice the stalks into very thin slices on the diagonal and place in a medium-size bowl. Finely chop the celery leaves and add to the bowl. Add the parsley and onions, and stir to combine.
In another small bowl, whisk together the vinegar, lemon juice, mustard, salt, celery seed and sugar. Drizzle in the oil, whisking constantly to emulsify the dressing, then slowly add the sour cream. Stir the dressing into the celery, parsley and onions.
Refrigerate the salad, covered, for at least 4 hours before serving to allow the flavors to develop.