Whisk dressing ingredients in a large bowl to blend. Add fennel and red onion; let stand 15 minutes to soften slightly.
Add remaining ingredients and walnuts; toss to mix. Transfer to a serving bowl.
**PLANNING TIP: The walnuts can be candied up to 4 days ahead. Store airtight at room temperature. The dressing and salad ingredients can be prepared to 8 hours ahead. Bag separately and refrigerate. Toss salad with dressing just before serving.