1. Place spinach, carrots, orange segments, and scallions in large bowl.

2. In small nonreactive bowl, combine vinegar, shallot, mayonnaise, mustard, salt, and orange zest. Whisk until mixture appears milky and no lumps remain. Place oils in liquid measuring cup so they are easy to pour. Whisking constantly, very slowly drizzle oils into mixture. If pools of oil gather on surface, stop addition of oils and whisk mixture well to combine, then resume whisking in oils in slow stream. Vinaigrette should be glossy and lightly thickened.

3. Pour dressing over spinach mixture and toss to coat; sprinkle with sesame seeds and serve immediately.

Serves 6 as a First Course