Beer-Braised Carnitas

Toast chiles in a dry large heavy pot over medium heat until slightly puffed and lightly darkened on both sides, about 2 minutes. Remove from pot; let cool. Stem chiles and halve lengthwise; discard seeds. Bring chiles, pork, beer, garlic, salt, and 1 cup water to a boil in same pot. Reduce heat, cover, and simmer, stirring occasionally, until pork is fork-tender, 60-80 minutes. Uncover pork; simmer until liquid evaporates and pork begins to brown, 20-25 minutes. Continue to cook, stirring frequently and scraping bottom of pot, until pork is shredded and browned, 10-15 minutes. Add 1 cup water to pork; cook, scraping up browned bits from bottom of pot, for about 1 minute. DO AHEAD: Carnitas can be made 3 days ahead. Let cool. Cover and chill. Reheat with 1/2 cup water in a covered pot, adding more water if needed to keep pork moist.