In a medium skillet, bring the water to a boil. Add the mushrooms and boil over high heat until all of the water has evaporated, about 4 minutes. Add the fish sauce and cook, stirring, for 1 minute. Transfer the mushrooms to the mortar and pound until coarsely mashed with the shallots and chiles. Transfer the mushroom-chile sauce to a bowl and stir in the tomato, cilantro, dill and sliced scallion. Season with salt and serve.