Preheat a large skillet over medium-high heat. Drizzle with olive oil.
In a medium bowl mix together ground beef, egg, garlic, onion powder, paprika, chili powder, salt, and pepper.
Form 6 thin patties. Add to the hot skillet, cooking for about 4 minutes per side, until the internal temperature reaches 145 degrees.
While the burgers cook, heat a small skillet over medium-high heat and drizzle with olive oil. Once hot, add onion and mushrooms, sautéing for 10 minutes, or until they've cooked down.
Spread a thin layer of mayonnaise on one side of each piece of Texas toast. On the side that does not have mayo, layer a piece of cheese, 1/6 of the onion mixture, a cooked patty, and top with another piece of cheese. Cover with a slice of bread, mayonnaise side up.
Heat a large skillet over medium heat. Once warm, add assembled patty melt, and cover. Cook for about 4 minutes per side, until golden brown and the cheese is melted.
Serve with barbecue sauce or ketchup!
Notes
I add onions and mushrooms to my patty melt, but you can add tomatoes, spinach, or even peppers to yours.