01 -
Melt butter in a medium skillet over medium-low heat. Add thinly sliced onions and cook, stirring frequently, until caramelized, approximately 15-20 minutes. Add water as needed to prevent burning. Remove onions and keep warm.
02 -
In a large bowl, combine ground beef, Worcestershire sauce, garlic powder, salt, and black pepper. Form mixture into 4 square patties, slightly larger than bread slices and about ¼ inch thick.
03 -
Heat a cleaned skillet over medium-high heat. Cook patties in batches (two at a time) for 1-2 minutes per side until seared. Remove from skillet and set aside.
04 -
In a small bowl, mix mayonnaise, lemon juice, black pepper, minced garlic, fresh parsley, and ketchup until combined.
05 -
Top 4 slices of Texas toast with a slice of cheddar, a burger patty, caramelized onions, pickles, tomato slices, another slice of cheddar, bacon, aioli spread, and a second slice of toast. Spread 1 teaspoon mayonnaise on the top slice.
06 -
Heat skillet to medium. Place sandwiches mayo-side down in batches (two at a time). Press down with a weighted pan to firmly hold sandwiches. Cook 3 minutes until golden brown, remove weight, spread 1 teaspoon mayonnaise on the top slice, flip sandwiches, and cook an additional 3 minutes until golden and warm throughout. Serve immediately.