In a large bowl, place all ingredients for the burger patties and mix together to combine. Be careful not to over-mix.
In a separate bowl, mash all ingredients for guacamole together.
Divide the burger meat into 4 equal sections.
Use your hands to divide each section in half. Flatten each half into similar sized circles, similar in diameter as a burger patty. Add a scoop of guacamole to the center of one circle, and top with the other circle. Pinch the sides to create a burger patty with the guacamole inside, shaping it the best you can. It's okay if guacamole seeps out of the edges a bit.
Repeat with the rest so you have 4 burger patties. If you don't use all of the guacamole, serve it as a topping with the cooked burgers.
Grease and heat the grill or a grill pan over medium high heat.
Cook the burgers for 4 minutes on each side, until cooked through.