01 - Heat 1 tablespoon of olive oil and 1 tablespoon of butter in a large skillet over medium-high heat until the butter melts and begins to shimmer.
02 - Add beef pieces in a single layer, season generously with salt and pepper, and sear for 2–3 minutes per side until a deep brown crust forms. Work in batches to avoid overcrowding the pan. Transfer browned beef to a plate and set aside.
03 - Reduce heat to medium. Add the remaining olive oil and butter to the skillet. Sauté the diced onions and mushrooms (if using) for 2–3 minutes until softened. Stir in the minced garlic and cook for 1 additional minute until fragrant.
04 - Sprinkle the flour over the vegetable mixture, stirring constantly for about 1 minute to cook off the raw flour taste and form a smooth roux.
05 - Slowly pour in the beef broth while stirring continuously and scraping up any browned bits from the bottom of the pan. Stir in the Worcestershire sauce and dried thyme until well combined.
06 - Bring the gravy to a gentle simmer. Return the seared beef and any accumulated juices to the skillet. Cook uncovered, stirring occasionally, for 8–10 minutes until the beef is tender and the gravy has thickened to your preferred consistency.
07 - Taste the gravy and adjust salt and pepper as needed. Sprinkle with fresh chopped parsley and serve hot over rice, mashed potatoes, or egg noodles.