Optional: sliced red onion, lettuce, tomato or pickles!
Add black beans through lime zest into a large mixing bowl. Using your hands, mash together the black bean mixture. You want all the ingredients thoroughly combined. Mash at least 50% of the beans to help the burgers stay together, but leave some whole for good texture!
Slowly add in the crushed tortilla chips - mixing as you go. You want the black bean mixture to stay together in a mass when squeezed with your hands. You may not use all of the chips.
Form the burgers so they are about ½" thick. This makes about 4-5 burgers. Put burgers on a plate, cover with plastic wrap and refrigerate for at least 1 hour.
Heat the olive oil in a non stick skillet over medium high heat. Add 2-3 burgers at a time and cook for 1-2 minutes on first side. Flip and continue to cook for another 1-2 minutes on the other side. If you want cheese on your burger, add it now so the hot side facing up can melt the cheese! (Cover with lid to speed cheese melting).
While the burgers cook, cut up avocados into a small mixing bowl. Mash with the back of a spoon to form a chunky paste. Add in additional lime juice and salt if desired.
Assemble the burgers - top with avocado, red onion and lettuce or any other favorite topping! Serve immediately!