Heat a large skillet over high heat and add a drizzle of olive oil, ensuring it's hot but not smoking. Carefully add the beef strips in a single layer, searing for 1-2 minutes on each side until beautifully browned. Once done, remove the beef and place it on a warm plate, covering it lightly to retain heat while you prepare the rest of the dish.

In the same skillet, reduce the heat to medium and add a generous pat of butter, allowing it to melt. Next, add sliced onions and minced garlic, sautéing for about 2 minutes until fragrant. Toss in the mushrooms, cooking for another 3-5 minutes until they become tender and golden brown.

Stir in the Dijon mustard and beef stock, increasing the heat slightly to bring the mixture to a gentle simmer. Let it bubble for 3-4 minutes, allowing the sauce to reduce and thicken slightly.

Lower the heat to medium-low and stir in the sour cream, mixing until the sauce is creamy and well combined. Return the seared beef to the skillet, gently folding it into the sauce.

Spoon the Gordon Ramsay Beef Stroganoff over a bed of buttered egg noodles or fluffy rice. Garnish with freshly chopped parsley.