Crab salad with avocado

Finely slice the cucumber with a mandolin or sharp knife. Mix the crab meat with one tablespoon mixed lemon juice and zest, chervil and dill in a bowl. Season with salt and pepper. Adjust flavour with remaining lemon juice, if needed. Cut the avocado in half and remove the pip (holding the avocado gently in your hand, carefully whack the pip with the blade of a sharp kitchen knife to securely embed, then twist the knife in one direction to dislodge). Peel and slice. Drizzle over some lemon juice to prevent browning. Mix vinegar and oil and season. Toss the salad leaves and cucumber with the dressing. There will be barely enough dressing, just enough to lightly coat the leaves. Place on two plates with sliced avocado. Top with crab meat and serve with lemonwedges.