Baby arugula, endive and mushrooms are tossed in a homemade Champagne vinaigrette.
Whisk the mustard, vinegar, shallots, chives, 1/4 teaspoon salt and a few grinds of pepper together in a medium bowl. Gradually whisk in the oil to emulsify.
Combine the arugula, endives and mushrooms in a salad bowl, and toss with the vinaigrette. Serve immediately.