Add the onion and garlic to a food processor (a mini one works great) and process until finely chopped/minced. Set this aside. Process the shrimp also in a food processor, pulse until the shrimp is finely chopped.
In a small bowl add the seasoning and mix together.
In a medium bowl add all of the ingredients together and mix until well blended. Divide into 4 equal portions and form into burgers. Place in the refrigerator while making the avocado mayonnaise.
Heat olive oil in a skillet (enough oil to coat the skillet well) over medium heat. Place the shrimp burgers into the heated pan, cook for 5 minutes or until the shrimp is turning pink and the burger is turning lightly brown. Flip the shrimp burger and continue to cook on the other side for another 5 minutes. Take into mind that the time may differ, it depends on how thick the burgers are and every stove heats a little differently. Watch carefully so the burgers do not burn.