Cook the bacon in a skillet until crispy. Set aside.
Butter the buns and toast them lightly on the skillet.
Divide the ground beef into 4 equal balls.
Heat a cast iron skillet or griddle over medium-high heat. Place a beef ball down, cover with parchment paper, and smash thin with a spatula.
Season with salt and pepper. Cook for 2–3 minutes until crispy, then flip once. Add cheese and let it melt.
In a separate skillet, fry the eggs (sunny-side up or over easy).
Assemble each burger: bottom bun, beef patty with cheese, bacon, fried egg, and any extra toppings.
Top with the bun and serve hot.