Beef Stroganoff with Mushrooms in Cream and Mustard Sauce

Have ready a wide, heavy skillet about 30 cm in diameter, a saucepan with a capacity of about 2 l and a tight-fitting lid, and a plate for the seared beef. Pat the trimmed tenderloin dry and cut it across the grain into slices about 1 cm thick, then into strips 4–5 cm long and about 1 cm wide. Slice the mushrooms about 5 mm thick, finely dice the onion and finely chop the garlic. Measure out the sauce ingredients; put the sour cream in a small bowl for tempering later.

Put 280 g uncooked rice, 560 ml water and 2 g salt in the saucepan; cover and bring to a boil over medium heat. Reduce the heat to the lowest setting and cook, covered, for 12–15 minutes, until the rice has absorbed the water and the grains are tender but hold their shape; do not stir while it cooks. Remove the saucepan from the heat, leave it covered for 5 minutes, then fluff the rice with a fork and keep it covered until serving. Cooking and resting the rice happen alongside searing and making the sauce; you will have about 750 g cooked rice, one-quarter for each serving, without draining any water.

Divide the beef into three batches of 200 g and divide 4 g salt among them, seasoning each batch just before searing. Heat the empty skillet for about 2 minutes over medium-high heat, add 5 ml oil and lay the first batch in a single layer with space between the strips. Cook for 60–90 seconds without moving them, then turn and cook for another 30–60 seconds: the surface should brown, and the beef should not release a puddle of juice or simmer for a long time. Transfer to the plate and sear the other two batches the same way, adding 5 ml oil each time; you will use 15 ml in total. Reserve the beef and all its juices for the sauce.

Heat 10 ml oil in the same skillet over medium-high heat and add 200 g mushrooms, spreading them as flat as possible. Cook for 4–5 minutes, without stirring at first, then turning the slices, until the released moisture has evaporated and the mushrooms are distinctly golden; add 1 g salt only at the end and transfer the mushrooms to a bowl. Repeat with the other half of the mushrooms, the remaining 10 ml oil and 1 g salt. Keep the browned bits and fat in the skillet: they will enrich the sauce, but must not be black or burned.

Reduce the heat to medium-low, add 20 g butter and all the onion. Cook for 4–5 minutes, stirring, until the onion softens and turns translucent; add the garlic and heat for about 30 seconds more, without browning it deeply. Sprinkle in 15 g flour and stir for about 1 minute, until it coats the onion in a thin layer and no dry powder is visible.

Gradually pour in 250 ml stock, stirring thoroughly and scraping the browned bits from the bottom so no lumps form. Add 25 g mustard, 2 g salt, all the pepper and all the seared mushrooms; bring to a gentle boil over medium heat and cook for 3–4 minutes, stirring. The sauce should thicken slightly and coat a spoon, and the raw flour smell should disappear; keep the beef out of the skillet.

Remove the skillet from the heat and wait about 1 minute, until the sauce stops boiling. Stir 200 g sour cream in the small bowl, then add a total of 60 ml hot sauce from the skillet in three additions, mixing thoroughly each time; use part of the sauce you have already made, without any extra liquid. Pour all the tempered sour cream back into the skillet and stir, then heat over low heat for about 1 minute. The sauce should be smooth, pale and hot; do not bring it to a vigorous boil, which could curdle the sour cream.

Add all the beef and its juices from the plate to the sauce and stir gently. Heat over low heat for 1–2 minutes, only until evenly warmed through, without vigorous boiling: the strips should stay tender and juicy. Cut through one of the thicker strips; its center should be hot, with no cool, raw interior. As soon as the beef is ready, remove the skillet from the heat so the tenderloin does not toughen.

Divide all the cooked rice among four plates and spoon the stroganoff alongside, dividing the beef, mushrooms and all the sauce evenly. Serve immediately, while the rice is fluffy and the beef is hot and tender.