Cut crosswise into 8 equal sized medallions, season with salt and pepper on both sides.
In a large pan, heat 1 tablespoon of olive oil on medium-high until hot. Working in batches if necessary, add the seasoned beef; cook 2 to 4 minutes per side for medium-rare, or until browned and cooked to your desired degree of doneness. Leaving any browned bits (or fond) in the pan, transfer to a plate. Let rest for at least 5 minutes.
While the beef rests, add 1 tablespoon of olive oil to the pan of reserved fond; heat on medium-high until hot. Add the diced shallot and remaining rosemary leaves; season with salt and pepper. Cook, stirring constantly, 30 seconds to 1 minute, or until fragrant. Add the vinegar (be careful, as the liquid may splatter); cook, stirring constantly, 30 seconds to 1 minute, or until the liquid has cooked off. Add the broth and cook, stirring constantly and scraping up any fond, 30 seconds to 1 minute, or until the liquid is slightly reduced in volume. Turn off the heat and stir in the butter until melted. Season with salt and pepper to taste.