Beef Stroganoff

Slice 260g beef sirloin into 5mm thick pieces against the grain.

Season evenly with 0.5 teaspoon salt and rest at room temperature for 10 minutes so the beef is not cold when it hits the pan.

Melt 1 tablespoon butter in the pan over high heat, wait for the foam to subside, then spread the beef slices flat in a single layer and sear for 1 minute per side until the outside is browned while the inside remains pink. Remove immediately to avoid overcooking.

Finely dice 80g onion into the same pan over medium heat and cook 4 minutes until translucent, then quarter 120g mushrooms and add them. When liquid begins to release, raise to high heat and cook 4-5 minutes until the moisture evaporates and the mushrooms turn golden brown with the oil visible again.

Sprinkle in 1 tablespoon flour, stir well, and cook for 1 minute to eliminate the raw flour taste, then pour in 180ml beef stock in a slow stream while whisking or stirring vigorously to prevent lumps. Cook until the sauce is smooth and glossy.

Stir in 1 tablespoon Dijon mustard and simmer over medium heat for 2 minutes until its sharpness distributes evenly through the sauce. The sauce should flow slowly off the back of an inverted spoon. Reduce to the lowest heat setting.

Add 120ml sour cream a little at a time while stirring to blend it smoothly into the sauce, keeping the heat at the lowest setting throughout. Return the beef to the pan and warm for 2-3 minutes until heated through. Do not let the sauce boil, or the sour cream will separate.