Put the tangerine juice in a small non-reactive saucepan
and bring to a boil. Cook until reduced to 1/2 cup. Let cool to room temperature.
the tangerines, removing all the white pith
, and segment over a bowl to catch both the segments and the juices. Cover and refrigerate until very cold.
Combine the reduced juice, tarragon
, egg yolk, and salt and pepper, to taste, in a blender
and blend until well mixed. With the machine running, add the 1 cup olive oil, at first by drops and then, as mixture emulsifies, in a thin, steady stream until all the oil is incorporated. Taste, for seasoning. Scrape into a jar, cover, and refrigerate until needed. You should have about 1 2/3 cups mayonnaise. Keeps 2 to 3 days, refrigerated.
Prepare the grill and let burn down to medium coals. Toss the cooled asparagus with about 1 tablespoon olive oil and season with salt and pepper. Grill over medium to low coals, turning the spears as needed, until they take on a little color and are just tender, about 6 minutes. Cover the grill
, if necessary, to maintain the heat.
Arrange the asparagus
on a platter with the reserved tangerine segments. Dot
with the mayonnaise
, and drizzle
with any tangerine juice left in the bowl. Garnish
with fresh or candied zest and the nuts, if using. Serve at once.
Cook's Note: Every cook has insecurities. One of mine is mayonnaise. I always get a little anxious until I see it coming together in the blender. If the mayonnaise is too thick, thin it, with the machine running, by pulsing in a little cool water. If you are concerned about raw eggs
, use a pasteurized egg product or an egg substitute
such as Egg Beaters.