1. Prepare the fennel by cutting bulbs in half lengthwise, trimming off feathery green leaves and reserving for garnish.
2. Slice fennel very finely and place the slices in a large bowl.
3. Quarter apples, remove cores and cut apple quarters into thin slices.
4. Add apple slices and nuts to fennel.
5. In a small bowl, combine mayonnaise and orange juice such that smooth and season with salt and pepper.
6. Toss the dressing with salad to coat.
7. Garnish with reserved fennel leaves and serve immediately with cold roast meat or cold poached fish.