Heat oven safe skillet on medium high heat. Make sure that the pan is large enough to hold all four steaks at once. Add Extra Virgin Olive Oil and allow pan to heat about one minute more.
Place steaks in the skillet. You should hear a sizzling sound. Cook until golden brown. Flip each steak over and place the whole pan into the oven. Cook until the steaks reach your desired doneness.
Place steaks on a plate to rest for at least 5 minutes.
Place the skillet back onto a burner on medium high heat. Deglaze the pan with the Dry Sherry, being sure to scrape the bottom of the pan thoroughly. Add the shallots and cook until fragrant.
Add the mustard, mixing thoroughly. Add tamari and beef stock and bring to a simmer.
Cook until slightly thickened (thick enough to coat the back of a spoon). Serve this pan sauce over the steaks.