To make the honey-mustard dressing, place the vinegar, honey, mustard and oil in a screw-top jar and shake until well combined. Season.
Arrange blueberries, blackberries, cucumber, avocado and rocket on a serving platter and drizzle with half the dressing. Top with salmon and goat’s cheese. Drizzle with remaining dressing. Sprinkle with hazelnut to serve.
