Both celery root and mussels are at their best right now, so here’s a bright-green menu that welcomes them — a cool weather meal with verve and brightness, best eaten near the warmth of a fire or reasonable facsimile thereof.
This dish employs two kinds of celery: the tender hearts of branch celery and so-called knob celery, also known as celery root or celeriac.
At the vegetable stand, knob celery is usually sold scrubbed, but still may look scary with its undeniably gnarled root. Fear not: That root is easily peeled with a sharp knife. Once the rough exterior is removed, a pale perfumed vegetable appears, ready to be shredded for a salad or cooked.
For a nice salad in winter, I cut the knob celery into matchsticks and give the strips a soak in salty lemon juice. Then, they are dressed with a thick mustardy vinaigrette, similar to what is called rémoulade sauce in France. Sharp mustard in the dressing complements the sweet celery-flavored root.
I like the crunchy addition of chopped celery hearts, the pale ribs at the center of green stalk celery. Paired alongside the root and sprinkled with thinly sliced scallions, the two vegetable cousins look good together, and what results appears and functions rather like a potato salad. Add chopped capers, cornichons, chives or tarragon to customize it; the mixture will keep for a few days at the ready in the fridge. Spicy watercress, arugula or radicchio leaves are perfect to perch the dressed salad upon when serving.