The distinctive and contrasting flavors of fennel and radicchio need only the lightest of dressings.
Whisk together vinegar, broth, oil, mustard, salt and pepper in a small bowl.
Trim stalks, stems and tough outer layer from fennel. Cut in half lengthwise, cut out core and thinly slice the fennel. Place in a bowl and cover with cold water. Let soak for about 10 minutes. Drain and place in a salad bowl. 3. Wash radicchio and cut into thin julienne strips. Add to the fennel. Drizzle the dressing over the salad and toss.
Make Ahead Tip: Cover and refrigerate the dressing (Step 1) for up to 2 days.