01 -
Heat a cast iron skillet over medium-high heat for 5 minutes until it begins to smoke lightly.
02 -
Divide ground beef into 4 equal portions (approximately 4 ounces each). Place one portion in the skillet and press down with a spatula to form a 1/4-inch thick patty. Repeat with remaining portions, cooking in batches if necessary.
03 -
Season the smashed side with kosher salt and freshly cracked pepper. Cook without disturbance for 3 minutes until edges are browned and crispy. Flip patties, add cheese slices on top, then cook an additional 2 to 3 minutes until cheese melts.
04 -
Slice croissants horizontally and evenly spread butter on cut sides. Toast butter-side down in a separate pan or the same skillet for 2 to 3 minutes until golden and flaky.
05 -
Place each cooked patty on the bottom half of a toasted croissant. Add optional toppings and sauces as desired, then cover with the top croissant half. Serve immediately.