Peel the shrimp, keeping the tails; rinse, dry. Coarsely chop the oyster mushrooms. Cut the chili lengthwise, remove the seeds, cut into large enough. Cut the lemongrass diagonally into small pieces. Peel and grind galangal. Pour the broth into a saucepan, bring to a boil, add mushrooms, kafir, galangal and lemon grass. Let it boil, add shrimp. When the shrimp begin to change color, add the chili paste. Stir, bring to a boil again, season with fish sauce, lemon juice and fresh chili, remove from heat. Sprinkle with green cilantro.