Mix the ground beef, breadcrumbs, egg and all the seasonings in a large bowl until combined, and form the mixture into burger patties.
Heat the oil in a large frying pan on medium heat, and fry the patties for 4-5 minutes on each side.
When you flip the burger to the other side, put a slice of cheese on the patty and let it melt while the patty is cooking.
Cut the buns open and add lettuce, a burger patty topped with cheese and, finally, a teaspoon of guacamole.
Notes
Use meat with a good ratio of lean ground beef to fat. The fat in the meat creates that juicy texture you want your burger to have. I believe the best ratio of lean meat to fat is 85/15: 85% lean meat, 15% fat.