How to Make It
Remove stems and seeds from chiles; discard. Rinse the chiles with cold water; drain. Arrange chiles in a single layer on a baking sheet. Broil 20 seconds on each side or until lightly toasted (be careful not to burn chiles).
Bring 4 quarts water to a boil in a large Dutch oven over medium-high heat. Stir in chiles, and cover. Remove from heat, and let stand 30 minutes or until soft. Drain.
Place half of chiles, 2 1/2 cups broth, and garlic in a blender; process until smooth. Pour the pureed mixture into a large bowl; repeat procedure with remaining chiles and broth. Strain chile mixture through a sieve into a large saucepan, and discard solids. Stir in salt. Cook over medium heat 30 minutes, stirring occasionally.