teaspoon strong Dijon mustard
Coarse salt and freshly ground pepper
tablespoon red- or white-wine vinegar
tablespoons peanut, sunflower, or grapeseed oil
Place mustard in a medium bowl; season with salt and pepper and whisk to combine. Slowly whisk in vinegar. Whisk in oil in a slow, steady stream until emulsified. Season with salt and pepper and add a splash or two of vinegar if necessary. Vinaigrette may be kept in an airtight container, refrigerated, for up to 1 week.