In a bowl that will take the crab meat later, whisk together the mirin, wasabi paste, rice vinegar, sesame oil and salt. Then remove about 4 teaspoons to another big bowl large enough to fit your salad.
To the first, more generous amount of dressing, add the finely chopped chilli and then the crab meat, and fork through to mix thoroughly.
To the small amount of dressing in the other bowl, add the lime juice and then the salad leaves and toss well to mix, before arranging on four plates.
Spoon a quarter of the mixture into a metal American ⅓-cup measure, or a small ramekin, squishing down to get it all in, then unmould in the centre of a salad-lined plate.
Just turn over, tap and the crab meat should fall out. Repeat with the remaining crab meat and the 3 other plates.
Using a rounded teaspoon measure, scoop out curls or humps of avocado and dot around on top of the salady bits. Spritz with a little lime juice.
Sprinkle the chopped chives over the mounds of crab and take the plates to the table.
