In a skillet, heat 2 tablespoons of olive oil over medium heat. Add sliced onions and a pinch of salt, then sauté for about 10 minutes until they are golden and caramelized.

In a large bowl, combine 1 pound of ground beef with salt, pepper, and half of the minced garlic. Form the mixture into patties slightly larger than the sourdough slices.

Push the caramelized onions to the side of the skillet and add the patties. Cook each side for about 4-5 minutes, topping them with cheese until melted.

In a small bowl, mix the remaining minced garlic with 4 tablespoons of softened butter and dried herbs to create garlic herb butter.

Heat another skillet and spread garlic herb butter on one side of the sourdough slices. Toast for about 3-4 minutes until golden brown.

Assemble the sandwich: place one slice of toasted bread, layer with the cheesy patty, add caramelized onions, and top with another slice of toasted bread.