1/2 cup fresh lemon juice, plus juice from 1/2 lemon for acidulated water
2 medium fennel bulbs
2 cups Sylvetta or other wild arugula
1 tablespoon Dijon mustard
¾ cup olive oil
Salt and freshly ground black pepper
Cut fennel in half and take the core out of the fennel.
Fill a medium bowl with ice water and add juice of half a lemon. Using a mandolin, shave the fennel into very thin slices across the grain. Transfer to the bowl of acidulated ice water.
Whisk the mustard and ½ cup lemon juice in a medium bowl. Slowly stream in olive oil while whisking to emulsify dressing.
Once the fennel has crisped up, remove from the ice water and drain on a paper towel. Place in a medium-sized bowl.
Add the arugula to the bowl with fennel and dress with the vinaigrette. Season with salt and pepper. Dressing the salad should take place immediately prior to serving.