Cut avocados in half and remove the pits. Scoop out avocado and place in a medium bowl, mash with a fork until there are small lumps. Fold in onion, jalapeño, lime juice and garlic. Line a baking pan with parchment paper. Spoon avocado mixture onto the pan and spread in an even layer. Cover with another layer of parchment on top. Freeze until solid (6-8 hours). Remove frozen mixture, uncover and cut into small cubes. Dip each cube in cornstarch, eggs, then panko. Repeat dipping in egg and panko again. Place coated cubes back onto the baking pan; and refreeze until firm (20-30 minutes). Heat oil to 330°F. Fry in batches, turning to brown evenly (2-3 minutes total). Drain on paper towels.