01 - Pat steaks thoroughly dry with paper towels. Season both sides generously with kosher salt and freshly ground black pepper, pressing gently to adhere.
02 - Heat olive oil and 1 tbsp butter in a large skillet over medium-high heat until butter foams. Add steaks and sear for 2–3 minutes per side for medium-rare, or until desired doneness is reached. Transfer to a plate and tent loosely with aluminum foil to rest.
03 - Reduce heat to medium. Add remaining 2 tbsp butter to the skillet. Add sliced mushrooms and sauté for 3–4 minutes, stirring occasionally, until softened and lightly browned.
04 - Add diced shallots and minced garlic to the mushrooms. Cook for 1 minute, stirring constantly, until fragrant and shallots begin to translucent.
05 - Stir in Dijon mustard, then carefully pour in brandy. Let simmer for 1–2 minutes, allowing alcohol to reduce slightly and cook off, scraping up any browned bits from the pan bottom.
06 - Pour in beef broth, Worcestershire sauce, and heavy cream. Simmer for 3–5 minutes, stirring occasionally, until sauce thickens enough to coat the back of a spoon.
07 - Return steaks and any accumulated juices to the skillet. Spoon sauce generously over the steaks. Cook for 1–2 minutes just to heat through. Sprinkle with fresh parsley and serve immediately with extra sauce on the side.