In a small bowl, whisk together the mustard, garlic, vinegar, 1 teaspoon salt, and 1/2 teaspoon pepper. While whisking, slowly add the olive oil until the vinaigrette is emulsified.
Place the salad greens in a medium bowl and add enough dressing to moisten. Sprinkle with a little extra salt and pepper, if desired, and serve immediately.
2008, Ina Garten, All Rights Reserved