In a small saucepan over medium heat saute onions in the oil. Cook until
softened, about 4 minutes. Set aside.
In a large bowl, combine cooled onions, ground beef, adobo sauce, chipotle
pepper, egg, bread crumbs, parsley, salt and sugar. Mix together thoroughly.
Form the meat mixture into 6 burgers. Heat a large saucepan and add a little
oil. Add burgers and cook until desired doneness.
Serve the burgers with diced avocados and if desired sour cream.