2 tablespoons canned chipotle chiles in adobo, including sauce
1 lb ground beef chuck
1/2 cup finely chopped onion
1 teaspoon salt
4 English muffins or hamburger buns, halved horizontally
Prepare grill for cooking over medium-hot charcoal (moderate heat for gas); see "Grilling Procedure," below.
Meanwhile, open any whole chipotles and discard seeds, then mince chipotles.
Mix chipotles (with sauce), beef, onion, and salt with your hands, then form mixture into 4 (3/4-inch-thick) patties.
Grill burgers on lightly oiled grill rack, covered only if using gas grill, turning over once, 4 minutes total for medium-rare. Grill English muffins, cut sides down, until grill marks appear, about 30 seconds. Serve burgers in English muffins.