In individual dishes or a large dish, fill half way with grey salt and make 4 footprints using an avocado. Preheat oven to 450ºF/230ºC and heat the prepared molds.
Halve avocados without damaging the shells as you need them for your filling. Remove pits and scoop out the flesh. Pass through a sieve and blend well, and add the zest of 1/2 lime and vanilla. Meanwhile, beat egg whites with cream of tartar; add sugar gradually. Beat meringue until stiff peaks and fold in avocado mixture. Place avocado shells in hot grey salt footprints. Pipe out some avocado filling inside each shell, add a couple of chocolate disks and top with a generous amount of filling. Fill up greased ramekins if you end up with extra avocado filling.
Bake at 450ºF/230ºC for 8 min. Dust with powdered sugar and serve immediately!