Preheat the griddle to high heat and add a splash of oil.
Generously season the steak on all sides. (Optional: dry brine ahead of time using high-quality salt for deeper flavor.)
Add about 50g of butter to the griddle and let it melt into the oil.
Place the steak onto the hot griddle, directly into the butter. Press down gently (a grill press can help) to ensure even contact and develop a deep crust.
Cook, turning the steak regularly to build a rich, even crust on all sides.
Add the crushed garlic, rosemary, and additional butter as needed. Baste the steak with the melted butter and aromatics as it cooks.
Use a meat thermometer to check doneness. For medium-rare, aim for an internal temperature of 52–54°C. (The temperature will continue to rise slightly as it rests.)
Remove the steak from the griddle and allow it to rest for a few minutes.
Slice across the grain and spoon over any remaining butter, garlic, and herbs from the griddle.