1) Pit and peel the avocado and cut it into 1.5cm chunks. In a small bowl toss the avocado chunks gently with 1 tbsp of the lemon juice and season with salt to taste. In a medium bowl, whisk together remaining lemon juice, 1 tsp Dijon mustard, pinch of white pepper, and 1/4 tsp salt. Add crabmeat and toss.
2) Stand an empty can with both top and bottom removed on a serving plate. Scoop a quarter of the avocado into the can. Place a quarter of the crabmeat on top and press down gently into the mold. Gently pull the can off the avocado and crab mixture. Garnish with a half tsp of chives. Repeat with the remaining 3 servings and serve.