Mimosa is a classic French garnish of sieved hard-cooked eggs that is frequently used for asparagus and leeks. Tarragon, which has an affinity for both asparagus and eggs, enhances the sherry vinaigrette.
- Put the eggs in a saucepan and cover by 2 inches with cold water. Bring to a boil over high heat, uncovered. Remove from the heat, cover, and let the egg stand for 20 minutes. Remove and let stand 5 minutes in cold water. Peel and cut the egg in half. Remove the yolk. Press it through a fine sieve and set aside in a small bowl. Finely chop the egg whites and set these aside in a small bowl.
- Trim the asparagus by bending until it snaps. Discard the lower, woody portion. Trim the broken end on a diagonal. Fill a large saucepan half full with water and bring to a boil over high heat. Add the asparagus, and reduce the heat to medium high. Cook between 45 seconds and 2 minutes, depending on size and maturity of asparagus. It should be bright green and retain a little crunch. Remove to a bowl with ice cubes and cold water and chill. Remove and pat very dry. Arrange on a platter.
- In a bowl, combine the olive oil and mustard, whisking together. Add the vinegar, minced onion, salt, pepper and tarragon. Arrange the asparagus on a platter, and pour the vinaigrette over it, coating it well. Set aside at room temperature for up the 30 minutes before serving.
- To serve, sprinkle half with sieved yolks, and half with the chopped egg whites.