Thai-Style Chicken Soup with Basil

 Ingredients2 fresh lemongrass stalks, root end trimmed and 1 or 2 outer layers discarded 2 large shallots, thinly sliced 2 large garlic cloves, thinly sliced 2 tablespoons vegetable oil 2 quart rich and flavorful chicken stock ; 1 or 2 outer layers discarded 1 (14-ounce) can diced tomatoes in juice, drained, reserving juice 2 ounces tamarind from a pliable block (a 2-inch cube), chopped 3 tablespoon Asian fish sauce 2 (2-inch-long) fresh Thai chiles, thinly sliced 2 fresh or frozen Kaffir lime leaves 1 (2-inch) piece peeled ginger, thinly sliced 1 pound skinless boneless chicken breast 1/4 pound snow peas, sliced 1/4 inch thick 1/3 cup packed basil leaves (preferably Thai) Accompaniment: cooked jasmine rice
PreparationCut off and discard top of lemongrass, leaving 6-inch stalks, then finely chop. Cook lemongrass, shallots, and garlic in oil in a large heavy pot over medium-low heat, stirring occasionally, until well browned, 12 to 15 minutes.
Add stock, reserved tomato juice, tamarind, fish sauce, chiles, lime leaves, and ginger and simmer, uncovered, 30 minutes.
While soup simmers, freeze chicken breast just until slightly firm, 20 to 30 minutes, then thinly slice crosswise.
Strain stock through a fine-mesh sieve into a large saucepan, pressing hard on and then discarding solids. Return to a simmer and stir in chicken, diced tomatoes, snow peas, and basil. Gently simmer just until chicken is cooked through, 1 to 2 minutes. Season with additional fish sauce and salt.