Trim off the root part of the mushrooms and separate them as much as you can. Put them in a container and set aside. Do not wash them.
Put the Sichuan peppercorns and dried chilies in a wok. Toast the spices over low heat. Keep tossing the spices around the wok making sure not to burn them. When you start smelling the fragrance from the spices turn the heat off then let cool for a while. When the spices are cool to touch pour them into a blender and pulse a few times until they are pulverized. They don’t have to be ground into a fine powder. Pour the spices into a bowl and add the sea salt. Mix well and set aside.
Prepare the batter by first mixing the flour, cornstarch and salt together in a mixing bowl. In a separate bowl whip the egg white into soft peaks and set aside. Now add icy cold water into the flour and cornstarch mixture and blend. Don’t worry if the resulting batter is a little lumpy. Pour this batter slowly into the whipped egg white and mix well.
Heat the vegetable and sesame oils together in a wok. The oil should be heated to the point when a drop of the batter sizzles in the oil. Separate the mushrooms into four portions. Put one portion in a small mixing bowl and ladle about one quarter of the batter into it. Cover the mushrooms evenly with the batter and drop them into the hot oil. Fry the mushrooms for about three minutes and turn them over. Continue to fry for another minute. The fried mushrooms should be crisp and slightly yellow but not brown.
Drain the mushrooms on a paper towel and immediately start the next portion of the mushrooms. Work as quickly as possible so you can serve them hot. Sprinkle chopped scallion and cilantro over the mushrooms and serve with the Sichuan spice salt.