Heat grill and season meat on both sides with salt and pepper. In a 2-quart saucepan
, heat oil and add onions
, garlic and mushrooms, sauteing until translucent. Add wine
and cook until reduced by half. Meanwhile sear
meat on both sides, and grill
to about 128 degrees F internal temperature on an instant-read thermometer for medium-rare. Remove meat from grill and let rest. Whisk
demi-glace into wine reduction
and adjust seasoning of sauce with salt and pepper, as needed. Spoon the sauce over the grilled steaks and serve.