Serves 2 to 6 as part of a meal

1 (1 1/2- to 2-pound) whole tilapia, porgy, or red snapper, scaled, gutted, and cleaned
1 large stalk lemongrass, outer layer, bottom 1/2 inch and top 4 inches removed
2 cups kosher salt
1 egg white, beaten
1/2 cup Spicy, Tart Dipping Sauce for Seafood (See the recipe here: http://food52.com/recipes/24662)

SAUCE: (see that link for directions):

Makes about 1 cup
3/4 ounces fresh green Thai (about 14) or serrano (about 3) chiles
1/4 ounce cilantro roots, thinly sliced
1/2 teaspoon kosher salt
6 tablespoons lime juice (preferably from Key limes or spiked with a small squeeze of Meyer lemon juice)
1/4 cup Thai fish sauce
5 teaspoons granulated sugar
2 tablespoons coarsely chopped cilantro (thin stems and leaves), lightly packed