Mix together mayo and basil, cover with plastic wrap and refrigerate until needed.
Combine chicken, grated apple, salt, pepper, and garlic. Gently use hands to get a really good mix going, making sure that everything evenly distributed and everything is well incorporated. Divide meat mixture into 4 evenly sized balls. Flatten each ball into a patty that is roughly the size of your burger buns – maybe a little larger.
Brush one side of each burger with olive oil, flip over onto grill, brush the other side with olive oil. Grill over medium heat until fully cooked. This is poultry – please cook until well done!
While burgers are grilling, saute apple slices in olive oil and salt until they start to tenderize. You want a slight amount of crunch, but not TOO much!
To assemble the burgers:
Split the buns, spreading basil mayo on both halves of each bun. Arrange a layer of apple slices on top of the bottom bun half.. Top with burger, and a generous layer of gouda slices. Crown with top bun, enjoy!