At times, mustard is more welcome on burgers than catsup or salsa. We like this on chicken and veal burgers.
Whisk together the mustard, vinegar, sugar, and dry mustard in a small bowl. Slowly add the olive oil, whisking constantly, until incorporated. Stir in the herbes de Provence.
Serve immediately, or refrigerate for as long as 2 days. Whisk before serving.