Pat the steaks dry with paper towels and season generously on both sides with salt and black pepper. Allow them to sit at room temperature for about 10 minutes before cooking.

Heat 1 tablespoon of butter and the olive oil in a large skillet over medium-high heat until the butter melts and begins to foam. Add the steaks and sear for 3-4 minutes per side for medium-rare doneness, or until they reach an internal temperature of 130°F (54°C).

Remove the steaks from the skillet and transfer them to a plate; loosely tent with foil to keep warm while you prepare the sauce.

Reduce the heat to medium and add the remaining 1 tablespoon of butter to the same skillet. Add the minced shallot and sliced mushrooms, sautéing for about 4-5 minutes until the mushrooms are tender and golden brown.

Add the minced garlic to the pan and cook for another 30 seconds until fragrant, being careful not to burn it.

Remove the pan from the heat momentarily to safely add the Cognac or brandy. Return the pan to the stove and let it bubble for 1-2 minutes to cook off the harsh alcohol smell, scraping up any browned bits from the bottom of the pan.

Stir in the beef broth, heavy cream, Dijon mustard, and Worcestershire sauce. Simmer the sauce for 3-4 minutes, stirring occasionally, until it thickens enough to coat the back of a spoon.

Return the steaks and any accumulated juices to the skillet, turning them once to coat in the sauce. Let them warm through for about 1 minute.

Serve immediately, garnishing with fresh chopped parsley and spooning the extra creamy mushroom sauce over the meat.