Fill a saucepan halfway with water; Add 2 tsp salt; Bring to the boil over a high heat; Add the crab legs; Bring to the boil over a high heat again; Turn to a medium-high; Let the crab legs boil for minutes, varying with the size (small: 4-5 minutes; larger: 7-8 minutes; colossal: 15 minutes); Remove the crab legs with a pair of spring-action tongs; Drain them.
Pick up the crab leg and apply pressure to the crab’s major joint with a crab cracker; Run a crab zipper down the soft side of the shell in one sweeping motion; Pull the meat out (repeat the step for each joint of each crab leg) .
Rinse and drain bitter melons; Cut off any stems; Bisect them lengthwise; Scrape any seeds out; Cut them into pieces; Put them into a bowl; Marinate them with 2 tsp salt for 20 minutes; Rinse them under running water; Drain them.
Fill a wok with water; Bring to the boil over a high heat; Blanch the bitter melon for 1 minute; Remove them immediately and rinse them under running water till cool; Drain them; Turn off the heat.
Arrange the bitter melon into an electric blender; Add seasoning (1); Blend it into puree.
Set an egg separator over a basic glass bowl; Break an egg into the egg separator, draining the egg white into the bowl.
Add seasoning (2) into a mixing bowl; Mix.
Pour 1.8L water into a deep wok; Bring to the boil over a high heat; Add the bitter melon and the crab meat; Bring to the boil over a high heat again; Cook it over a high heat for 30 minutes; Turn to a medium heat; Gradually stir seasoning (2) into the soup; Bring to the boil over a medium heat; Turn off the heat; Gradually stir the egg white into the soup; Arrange it in a serving bowl; Ready to serve.