01 - Pat steaks thoroughly dry with paper towels. Season both sides generously with salt and freshly ground black pepper, pressing seasoning into the meat.
02 - Heat olive oil and butter in a large skillet over medium-high heat until butter foams and pan is thoroughly hot.
03 - Add steaks to hot pan. Sear for 2–3 minutes per side for medium-rare doneness, adjusting time as needed for preferred doneness. Transfer steaks to a plate and tent loosely with foil to rest.
04 - In the same skillet, add sliced mushrooms. Sauté for 3–4 minutes until golden brown. Add minced shallots and garlic; cook for 1 minute until fragrant.
05 - Carefully pour in brandy or cognac. If desired, carefully ignite with a long lighter to flambé and burn off alcohol. Let liquid reduce by half for 1–2 minutes.
06 - Stir in heavy cream, Dijon mustard, Worcestershire sauce, and fresh lemon juice. Simmer for 2–3 minutes until sauce thickens and coats the back of a spoon.
07 - Return rested steaks and any accumulated juices to the skillet. Spoon sauce generously over steaks and simmer for 1 minute to rewarm through. Sprinkle with chopped parsley and serve immediately.