Pat the beef strips dry with paper towels and season evenly with 1/2 tsp sea salt and 1/4 tsp freshly ground black pepper. Why: Removing surface moisture promotes an immediate, hot sear; light seasoning up front begins flavoring the meat but allows you to finish seasoning later.

Heat a large heavy skillet (cast-iron preferred) over medium-high heat for 2–3 minutes until very hot — you should see faint wisps of smoke when you’re ready. Why: A properly hot pan creates Maillard browning — the flavorful crust that gives the beef its roasted, savory notes.

Add 1 tbsp olive oil and 2 tbsp butter to the pan. Swirl to combine and let the butter foam. Why: A mix of oil and butter raises the smoke point while keeping the sauce-rich, buttery flavor; the foaming butter indicates it’s hot and ready to receive meat.

Add the beef strips in a single layer — do not crowd the pan (cook in two batches if necessary). Sear without moving for 1½–2 minutes to develop a deep brown crust, then flip and sear the other side 1–1½ minutes for medium-rare (adjust time for desired doneness). Why: Leaving the meat undisturbed allows the surface to caramelize; quick cooking keeps strips tender rather than overcooking them like a whole steak.

Transfer seared beef to a warm plate and tent loosely with foil. Why: Resting lets juices redistribute so the slices stay juicy when sauced.

Reduce heat to medium and add the remaining 2 tbsp butter to the pan. When it melts and foams, add the chopped shallot and 1/2 tsp salt; cook, stirring, 1½–2 minutes until softened and translucent but not browned. Why: Cooking shallots gently extracts sweetness for the sauce without adding bitter, burned flavors.

Add the minced garlic and cook 20–30 seconds, stirring — just until fragrant. Why: Garlic burns quickly; a short cook time releases its aroma without developing bitterness.

Pour in 1/2 cup beef broth and scrape the brown fond (browned bits) from the pan with a wooden spoon. Stir in 1 tbsp Worcestershire and 1 tsp Dijon. Bring the liquid to a gentle simmer. Why: Deglazing dissolves the caramelized fond into the sauce, which is full of concentrated flavor; Worcestershire and Dijon add umami and bright, tangy depth.

If you prefer a slightly thicker sauce, whisk 1 tsp cornstarch with 1 tbsp cold water to make a slurry and stir into the simmering sauce; simmer 1 minute to thicken. Taste and adjust seasoning with remaining 1/4 tsp salt and 1/4 tsp black pepper. Why: Cornstarch quickly thickens without clouding flavor; seasoning at the end accounts for reduction concentrating the sauce.

Return the beef and any accumulated juices to the pan; toss quickly in the sauce off the heat for 30 seconds to warm through and coat. Why: Finishing in the sauce melds flavors without overcooking the beef strips; off‑heat tossing preserves texture.

Plate the beef strips, spoon extra sauce over the top, and finish with a sprinkle of chopped parsley. Serve immediately. Why: Serving right away keeps the beef at ideal temperature and texture; fresh parsley adds a clean herbal contrast to the rich sauce.