Preheat broiler with oven rack 6 inches from heat. Place chiles in a single layer on a baking sheet; broil until well charred all over, 5 to 8 minutes. Transfer chiles to a large bowl, and cover with plastic wrap. Let stand 5 minutes.
Place garlic cloves on baking sheet; broil until browned, 3 to 4 minutes. Peel chiles and garlic; discard peels. Remove and discard seeds from chiles.
Place chiles, garlic, lime juice, and salt in a blender. With blender running on low speed, add oil in a slow, steady stream until mixture is smooth. Serve immediately or store in an airtight container in the refrigerator up to 3 days.