In a large bowl, combine the beef, pureed chipotles in adobo, salt, and onion. Hands are best for this.
Using 1/4 cup at a time, form the mixture into small patties.
Heat a grill pan over medium-high heat. Pan-grill the burgers for 3 to 3 minutes on each side until they are done to your liking. Serve on the buns (toasted if you wish) with the salad/slaw and some blue cheese dip.
Notes
To make pureed chipotles in adobo, simply buy a can of chipotles in adobo sauce, dump the whole thing into a food processor, and purée. The sauce will keep in a tightly covered container in the fridge for about 2 months, at least.