Briefly blanched green spears contribute to the crisp texture and fresh flavor of this crunchy asparagus slaw, which also includes sweet, nutty jicama, celeriac, and sharp radishes.
Snap off and discard tough ends of asparagus. Bring a large saute pan of salted water to a boil; prepare an ice bath. Blanch asparagus just until bright green, about 30 seconds. Immediately transfer to ice bath. Drain, and slice spears in half lengthwise.
Grate 1 teaspoon zest, and transfer to a bowl. Squeeze 2 teaspoons juice, and add to bowl. Add mayonnaise, heavy cream, and 2 teaspoons water; season with salt and pepper. Whisk until combined; set the dressing aside.
Place asparagus, celeriac, jicama, and radishes in a bowl; toss. Add dressing, chives, and thyme; toss. Garnish with thyme sprigs.