Mix together the dijon mustard, garlic, soy sauce, Worcestershire and pepper.
Using paper towels, thoroughly pat the venison steaks dry to remove blood. Spread all sides of the venison steaks with marinade. Lay the steaks on a plate and cover with plastic wrap. Let sit at room temperature for 1 hour (or refrigerate overnight).
Lightly pat the steaks dry again with paper towel to remove any excess marinade.
Heat a cast iron skillet over medium-high heat with 1 tablespoon of oil. Once hot, cook the steaks about 4-6 minutes on the first side, then flip and cook another 4-6 minutes, or until the internal temperature reaches about 130-135 degrees F for medium-rare (if the steaks are getting too charred, reduce heat to medium).
Note: The total time will vary depending on the thickness of the steaks. If the steaks are thicker than 1 inch, I like to use tongs to stand the steaks on their sides to sear each side about 1-2 minutes. Keep in mind that the internal temperature of the steaks will continue to rise about 5 degrees after removed from the skillet.
Once done, transfer the steaks to a clean plate. Loosely tent with tinfoil and let rest while you make the mushroom cream sauce.