We heat our large saute pan over medium heat while we generously salt and pepper the steaks. We add the oil to the pan and, when hot, we add the steaks. We cook for about 4-5 minutes per side. We want the meat to be about 130 degrees for medium-rare. When done, we remove the pan from the stove, remove the steaks from the pan, and then place them on a plate to rest for about 5 minutes while we make the sauce.
We place the pan we browned the meat in back over medium-low heat and add the garlic and shallots. We stir for about a minute and, taking the pan off the heat, we add the dry sherry. We replace the pan on the stove and stir for another minute, scraping up the brown bits with a wooden spoon. We want the pan to be almost dry when we add the mushrooms. We saute the mushrooms for a few minutes over medium heat and, when they are tender and have released their liquids, we add any jus (juice) accumulated on the plate the meat is resting on. We taste for salt and pepper and add the parsley. We heat on low for a few minutes and we have our topping for the steaks.