Shape the mixture into eight patties. Place on a plate and cover with plastic wrap. Chill for at least 1 hour.
In the meantime, prepare the sauces as you use them.
For the avocado aioli: Put the avocado, garlic, and lime juices in a blender or food processor. Puree until smooth. Add a little more lime juice or water if the mixture isn’t smooth. It should be the consistency of yogurt. Stir in the coriander and set aside.
For the coriander butter sauce: In a small saucepan, cook the vinegar until it is halved. Remove from heat and stir in the butter pieces until incorporated. Stir in diced tomatoes, coriander, salt and pepper to taste. Put aside.
How to cook the crab cakes: In a large pan, heat a few tablespoons of rapeseed oil over medium heat. Add four crab cakes to the pan and cook for 3 to 4 minutes, or until brown on each side.
To serve, top the crab cakes with avocado aioli and / or coriander butter sauce. Serve warm on a bed of mixed greens, if desired.
Nutritional information per serving (1 crab cake): 242 calories (58 percent from fat), 16 g fat (5 g saturated fat), 11 g carbohydrates, 15 g protein, 631 mg sodium, 87 mg cholesterol, 2 g fiber