Preheat your oven to 400°F (200°C). Cut the top off the head of garlic, exposing the cloves. Drizzle with 1 tablespoon of olive oil and wrap in aluminum foil. Roast the garlic in the preheated oven for about 30-35 minutes, until soft and caramelized. Remove and let cool.

In a bowl, combine the softened butter, miso paste, and the roasted garlic (squeezed from its skin). Mix until smooth and well combined. Set aside.

In a food processor, combine the chopped scallions, rosemary, and the remaining 3 tablespoons of olive oil. Pulse until finely chopped and mixed into a paste.

Pat the sirloin steak dry with paper towels and season generously with salt and pepper on both sides. Rub the scallion and rosemary mixture evenly over the steak, pressing it into the meat.

Heat a large oven-safe skillet over medium-high heat. Once hot, add the steak to the pan. Sear the steak for about 4-5 minutes on each side, or until a nice crust forms.

Transfer the skillet to the oven and roast for an additional 10-15 minutes for medium-rare, or until your desired doneness is reached.

Remove the steak from the oven and let it rest for at least 10 minutes before slicing. Serve slices of the sirloin topped with a dollop of the miso-roasted garlic compound butter.