Preheat the griddle to high heat and drizzle a small amount of avocado oil.
Roll the ground beef into 5-ounce balls and season with salt and pepper.
Melt about 1 tablespoon of butter on the griddle where you will cook the patties. Place the meatballs on the buttered surface, cover each with parchment paper, and press flat.
Season again with salt and pepper and cook for about 2 minutes before flipping.
On a low-heat section of the griddle, drizzle more avocado oil and add the drained corn. Stir occasionally and cook for a few minutes until lightly toasted.
Flip the burgers and place one slice of cheddar cheese on each patty.
On another low-heat area, spread 1 teaspoon of butter and place all four slices of sourdough bread on top. Toast each side for about 1 minute or until golden brown.
Remove the cooked burgers from the griddle and set them aside on a plate.
In a mixing bowl, combine 1 cup of guacamole, ½ cup of pico de gallo, and the cooked corn. Stir until evenly mixed.
Lay out the toasted bread slices to assemble the sandwiches. Spread about 2 tablespoons of the guacamole mixture on one slice of bread.
Place the cooked burger patties on top, followed by shredded lettuce and sliced red onion.
Spread about 1 teaspoon of chipotle aioli on the top slice of bread and place it over the sandwich.
Slice the sandwiches in half or diagonally. Stack one half on top of the other and secure with a toothpick.
Serve immediately and enjoy your Southwest Patty Melts!