Plunge the live crab into the pot of boiling water and cook for 10 minutes. Remove the crab and let rest for 30 minutes. Do not crack the crab before this as it is still cooking.
While the crab is resting cut the avocados down the centre and separate. To half the stoned ones firmly tap with the heel of the knife and twist to the side, the stone should be easy to remove otherwise scoop out with a spoon. Roughly chop and put into a blender with a squeeze of half a lemon and a good pinch of salt and blend until smooth.
Cut the peeled and deseeded tomatoes into small dice and dress with the chilli, extra virgin olive oil and salt.
Roughly chop the over ripe tomatoes and red pepper and add to a blender with a good pinch of celery salt and pinch of sugar. Blend so they crush well and then hang in a muslin cloth (it should run clear).
In a rolling pan of boiling water plunge your basil and leave for about 40 seconds, take out and immediately blend with as little water as possible. Once it is completely blended pass through a chinois.
The crab should be cooked but also at a temperature that is comfortable to handle. Take the claws and the legs off. Each leg and claw have joints which you can break down into smaller more manageable pieces. With the round side of a soon tap consistently on the same place of the shell until it cracks open, pull the shell off of the flesh but be careful to remove all of the shell including the feather bone on the inside and place the flesh in a clean bowl. Keep a bowl of water beside you as you work to help you remove small shell pieces off your fingers.
Once finished mix with lemon oil and salt if you feel it is needed.
Build each layer starting with the crab, then tomatoes and finally avocado puree into a round mold. Garnish with basil leaves on top. Finish by mixing the basil and the tomato consommés together and pour on just before eating.