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.
Grilling Procedure
Hot: When you can hold your hand there for 1 to 2 seconds
Medium-hot: 3 to 4 seconds
Low: 5 to 6 seconds
If using a gas grill, preheat burners on high, covered, 10 minutes, then, if necessary, reduce to heat specified in recipe.
If you aren't able to grill outdoors, burgers can be cooked in a hot well-seasoned ridged grill pan over moderately high heat, turning over once, about 7 minutes total for medium-rare.
