- 2 tablespoons yellow mustard seeds
- 1/2 cup white balsamic vinegar
- 1 tablespoon Dijon mustard
- 1/4 cup minced shallots (2 medium)
- 2/3 cup extra-virgin olive oil
- 2 large bunches watercress, thick stems trimmed (about 6 cups packed)
- 1 1/2 pounds celery root (celeriac), trimmed, peeled, coarsely grated in processor or with box grater
- 20 radishes, trimmed, thinly sliced
- Stir mustard seeds in dry skillet over medium heat until lightly toasted and starting to pop, about 3 minutes. Transfer to bowl; cool. Add vinegar, mustard, and shallots; whisk to blend. Gradually whisk in oil. Season with salt and pepper.
- Toss watercress in large bowl with enough dressing to coat lightly. Divide watercress among plates. Combine celery root and radishes in same bowl; toss with enough of remaining dressing to coat. Season to taste with salt and pepper. Top watercress with celery root mixture and serve.