Heat a tablespoon of olive oil in a large skillet over medium heat. Add thinly sliced onions and a pinch of salt, then sauté for about 10 minutes until they are golden brown and caramelized.

In a mixing bowl, combine ground beef with salt, pepper, and half of the freshly minced garlic. Mix gently but thoroughly, then form into patties slightly larger than the sourdough slices.

Push the caramelized onions to one side of the skillet and add the beef patties. Cook for 4-5 minutes on each side until nicely browned and the internal temperature reaches 160°F.

In a small bowl, mix the softened butter with the remaining minced garlic and your choice of dried herbs.

Once the patties are cooked, place a slice of cheddar cheese on each patty and cover the skillet. Allow them to sit for about 1 minute, or until the cheese is melted and bubbly.

In a separate skillet, spread the garlic herb butter generously on one side of each sourdough slice. Toast for 3-4 minutes until golden brown and crispy.

To assemble, lay a cheesy patty on one slice of the toasted bread, top with caramelized onions, then place another slice of bread on top, pressing gently to combine all the flavors.