Remove the leaves of the rosemary sprigs, then finely chop the leaves.
Rub the sirloin on both sides with olive oil.
Here's a tip, whenever you are using fresh ground pepper and olive oil is involved, ground the pepper into a small bowl first so you can just sprinkle with your oily hands. Rub both sides of the sirloin with the fresh ground pepper and kosher salt.
Now rub your sirloin steak with the finely chopped rosemary.
Now we want to let that steak sit at room temperature for about 30 - 45 minutes. This allows the sirloin to take on the flavor of the rosemary and also allows it to come to room temperature, enabling more even cooking.
Now fire that grill up on high heat, we are going to direct grill this delicious hunk of meat to sear in the juices. We are using direct heat for this recipe, so keep the lib open at all times.
Once the grill has heated up, place the sirloin on the hottest part of the grill. Leave it alone for about 2 minutes. NOTE: You might want to keep a squirt bottle or cup of water handy. The at from the steak and the olive oil will tend to cause flare ups. Splash a tiny bit of water on flames that last more than a few seconds so you don't char too much (a little charring is fine!).
Now pick the steak up with tongs (remember from our grilling tips, never pierce the meat with a fork!) and rotate 45 degrees to get those nice grill marks.
After 2 more minutes, flip the steak.
Grill for 2 more minutes (you are getting the hang of this now!) and then rotate again 45 degrees.
Grill for a final 2 - 3 minutes or until done.
Now remove the steak and place on a platter and LEAVE IT ALONE for at least 5 minutes. If you pierce that sirloin steak too soon after grilling, the juices will escape. Let it rest and the juices will redistribute. Garnish the platter with your left-over rosemary springs and serve!