In a small bowl, combine the shallot, chives, mustard, tarragon, chervil, parsley, capers, cornichon, vinegar, and grapeseed oil. Season with salt and pepper to taste.
In a medium mixing bowl, toss 1/4 cup of the vinaigrette with the turnip and radishes. Season with salt and pepper to taste.
Combine the mayonnaise, lemon juice, and cayenne in a medium bowl. Add 1/4 cup of the vinaigrette and mix well. Add the crabmeat and toss to coat.
To serve, divide the turnip-radish slaw among four to six chilled plates. Spoon the crabmeat on the top of the slaw, trying to keep the crabmeat lumps as intact as possible. Drizzle the Chive Oil around each plate, and garnish with chive blossoms if desired.
Yield: 4 to 6 servings