Heat a large stainless steel skillet over medium heat. Add the butter and olive oil and cook the onions, stirring often, until they are softened and nicely caramelized. If they start to brown too quickly, add a tbsp of water to the pan at a time. This will lift the caramelized sugars off the pan and put them back into the onions. The onions should shrink quite a bit and be very flavorful.

Heat a nonstick griddle and melt some butter in order to griddle the bread. Toast the bread on both sides.

Divide the ground beef into four portions and form them into patties that are roughly the shape of the bread. Sprinkle the patties with Worcestershire sauce and season with salt and pepper. Heat the stainless skillet over high heat and cook the burgers for 2-3 minutes on either side. Mine were quite thin and cooked very quickly. Brush the tops with bbq sauce.

To assemble, spread beer cheese onto one piece of toasted bread. Top with a burger patty and a layer of caramelized onions and another piece of toasted bread.