In a medium skillet, melt 3 tablespoons of butter over medium-low heat.

Add the thinly sliced yellow onions and cook until they caramelize, stirring often for about 15-20 minutes. Add water as needed to prevent burning. Remove the caramelized onions from the skillet and tent to keep them warm.

In a large bowl, mix together the ground beef, garlic powder, salt, and pepper.

Form 8 square patties, each about 1/4 inch thick.

Wipe out the skillet and set the heat to medium-high.

Add the hamburger patties in batches (two at a time) and cook for 1-2 minutes per side. Remove the patties from the skillet and set them aside.

Toast 4 slices of Texas toast and set them aside.

In a small bowl, combine the mayonnaise, lemon juice, pepper, minced garlic, fresh parsley, and ketchup to make the aioli spread.

Top 4 untoasted slices of bread with Gruyere cheese, a hamburger patty, caramelized onions, a slice of toasted bread with aioli spread on both sides, more cheese, a second beef patty, more onions, and finish with a slice of bread.

Spread 1 teaspoon of mayonnaise on the top slice of bread.

Wipe out the skillet and set the heat to medium.

Add the assembled sandwiches to the pan with the mayo side down.

Place a weighted pan on top to press the sandwiches firmly in the pan. Cook until golden brown, about 3 minutes.

Remove the weighted pan, spread 1 teaspoon of mayo on the top slice of bread, and flip the sandwiches carefully.

Cook for an additional 3 minutes, or until the sandwiches are golden brown.

Serve the French Onion Patty Melts while they’re warm and enjoy this flavorful delight.