Preheat your oven to 450 F. Heat the butter and olive oil in an oven-safe skillet over medium-high heat. Add in the sprigs of rosemary as your pan is heating. Salt and pepper the meat to your liking (I recommend a generous pinch of each, which is a THREE-finger pinch.)
When the butter has melted and the oil is heated, add your steaks to the pan to get a nice golden-brown sear on them. This should take about 2 minutes on each side. Then place your pan in the oven until the steaks are cooked to your preference, 7 to 9 minutes. (Eight minutes makes a perfect medium, my favorite!)
Allow the meat to rest 5 minutes before slicing and serving. These rosemary-infused steaks are nothing short of delicious.