This is very good on its own; you can also serve it with lettuces or other greens, either mixing them all together or topping the greens with the celeriac and radish combo. If you are going to use lettuces, then double the dressing ingredients.
4 c peeled, coarsely grated celeriac
1 to 1-1/2 c thinly sliced radishes
1 T mustard seeds, optional
4 T white wine or apple cider vinegar
1-1/2 t prepared mustard, such as Dijon
2 T chopped leeks or onion
6 T extra-virgin olive oil
salt and pepper, to taste
chopped fresh herb, for garnish, optional
1. Combine grated celeriac and radishes in a serving bowl.
2. If using mustard seeds, put into a small, dry skillet over medium heat until they start to pop. Cover and remove from heat. Let them cool.
3. Combine mustard seeds, vinegar, prepared mustard, leeks, olive oil, salt, and pepper in a small bowl. Pour over celeriac and radishes. Toss to combine. Sprinkle chopped fresh herb over all.