Preheat fan forced oven to 180C. Place the king crab legs in foil tray and a small amount of water. Seal with foil. Place in the oven for 10-12 minutes to stem through and warm up. Remove the meat from the crab legs and place in a small bowl. Break up any overly-large pieces with your hands.
Split the muffins in half horizontally. Place under the griller for 1 minute.
In a heatproof bowl set over a pan of simmering water, whisk egg yolks with water, whisking vigorously, until mixture thickens. Remove from heat, and stir in lemon juice. Whisk in 1-2 pieces of butter at a time until melted. Season with salt.
Bring a medium pot of salted water to a simmer. Crack the eggs into a small bowl. Using a large spoon, swirl the water in the pot and then gently tip the eggs into the center of the whirlpool. Use a slotted spoon to remove the eggs after about 3.5 minutes.
Build from the bottom up: English muffin, King Crab, poached egg, Hollandaise sauce.