Here, we add these special peppers twice – first to the mayonnaise, which gets spread on the buns, and then mixed into the meat before its grilled. And don’t skip the red onions and tomatoes: they add a sweet, crisp bite.
In medium bowl, stir together mayonnaise, 1 tbsp. chipotle sauce, 1 tsp. garlic, cilantro and adobo; cover and refrigerate until ready to use.
In large bowl, gently mix together beef, chopped chipotle, 3 tbsp. chipotle sauce, remaining garlic and adobo until combined. Divide meat into 6 portions; form into 1”-thick patties. (Take care not to over-handle meat or else it will toughen).
Prepare grill to medium-high heat, grease with oil (or heat oil in medium skillet over medium-high heat). Cook burgers, flipping once, until charred and cooked to desired doneness (about 12 minutes total for medium rare). Add cheese to patties about 5 minutes before taking them off grill.
To assemble, divide patties evenly among bottom buns; top with onion slice, tomato slice, lettuce and top bun spread with reserved chipotle mayonnaise.