Place the cannellini beans, fennel and celery in a small bowl. Drizzle with a little olive oil and sherry vinegar. Season with salt and pepper. Toss to combine and set aside.
Preheat oven to 200˚C, fan on. Place mushrooms on a baking tray. Drizzle with olive oil and season with salt, pepper and garlic powder. Roast for ± 7 minutes until tender and juicy, but retain some bite.
Allow the mushrooms to rest. Once the mushrooms have rested, assemble the salad.
Layer the baby leaves and apples on a serving platter. Spoon over the marinated bean mixture.
Top with the roasted mushrooms. Sprinkle with walnuts and fennel fronds. Season lightly.Drizzle everything with a little extra sherry vinegar and olive oil and serve!