1Combine ground beef, 2 tablespoons chipotle pepper sauce and salt in large bowl; mix well. Shape into 6 patties.
2Combine mayonnaise with remaining chipotle pepper sauce and mix well; set aside. Grill hamburger patties to desired doneness; place cheese slices on burgers and continue cooking just until cheese melts. Spread mayonnaise mixture on each cut side of buns.
3Top bottom half with burger, onion slice, tomato slice, avocado slices and lettuce leaf. Cover with bun top. Repeat for remaining burgers.