Bring the Sirloin steaks to room temperature 1 hour before cooking. For the rosemary sauce: Remove the fresh rosemary from the sprigs, wash and pat dry. Put in a pan with the olive oil, heat without letting it boil and remove from the heat. Let infuse for 30 minutes or more. Pre-heat the oven grill to 500ºF with the rack on the position nearest to the grill – it needs to pre-heat a minimum of 15 minutes to be really hot. Put the broiler pan in the oven to get it hot. Broil with the door of the oven slightly open otherwise it will cook the meat with the meat’s humidity and it won’t have the crispiness of a grilled steak. Depending on how you like your meat, cook for more or less time. Start checking after 5 minutes. Turn the steak over to grill the other side and allow to cook. Remove from the grill, put on the cutting board and slice the steak thinly. Put each sliced steak on warmed serving plates. Heat the Infused olive oil without letting it boil. Season with salt and fresh ground black pepper. Sprinkle the rosemary over the meat and drizzle the hot olive oil over the steak. And as this is a typical Tuscan recipe, serve with sautéed spinach as is the tradition.