This stroganoff cooks the sirloin as a whole steak before slicing, then adds it to the sauce only for a short warm-through. That distinction matters: it is a 55-minute meal for four, not a long beef braise. The 800 g potatoes can cook while the 600 g steak sears, and the mushroom pan sauce comes together during the steak rest. Save the sour cream for the lowest-heat stage.
Mushroom Beef Stroganoff with Potato Mash makes 4 servings, with 55 min estimated total time. View the standalone recipe page.
Start the potatoes and organize divided ingredients
Cover the peeled 3 cm potato pieces with cold water by 2 cm and add 3 g salt. Bring to a boil and simmer for 15–20 minutes until tender. Starting the pieces together in cold water helps the centers and outsides cook on a similar schedule. A fork or knife should pass into a piece easily before draining.
Divide the oil into two 15 g portions and the butter into 15 g for the mushroom pan and 25 g for the mash. The salt also has separate jobs: potatoes, steak, mash and sauce. Measuring these allocations now avoids using the entire amount during the first stage and then seasoning later components again.
Sear the sirloin whole and rest before slicing
Season the whole steak with 2 g salt and the pepper. Heat the first 15 g oil in a heavy frying pan over medium-high heat, then sear for about 5–7 minutes per side. The stated timing assumes steak about 2 cm thick. A thicker piece needs additional checking rather than being treated as interchangeable.
Measure 145°F / 63°C in the center before transferring the steak to a clean board. Rest for at least 3 minutes, then cut into narrow strips across the grain. Keep the board juices for the sauce. The later 1–2-minute warm-through is not a substitute for properly cooking and resting the whole steak first.
Let the mushroom moisture cook away
Lower the pan to medium and add the remaining oil, the smaller butter portion, onion and mushrooms. Cook for 8–10 minutes, stirring as needed. Mushrooms may first release liquid; let that stage pass so their surfaces can begin to brown. Pouring stock in immediately would turn this into a pale simmer instead of a browned mushroom base.
Stir in 10 g flour for 1 minute. Add the 200 ml stock gradually while stirring, then the Dijon mustard, and simmer for 3 minutes. Working the liquid in little by little helps disperse the flour instead of leaving dry pockets. Scrape useful browned residue into the sauce without preserving any burnt bits from an overheated steak pan.
Steam-dry the potatoes before mashing
Drain the cooked potatoes and let them steam-dry in their hot pan for 1 minute. Water clinging to the surfaces dilutes the milk and butter, so take this brief step before mashing. Add the 150 ml milk, remaining 25 g butter and 2 g salt, then mash until the texture is consistent.
Use a masher and avoid prolonged aggressive processing. You want a soft base that holds the sauce, not a sticky potato paste. Cover to keep warm while the stroganoff finishes. If the potatoes become ready early, finish them deliberately rather than leaving cooked chunks sitting in their water throughout the mushroom stage.
Temper the sour cream and warm gently
Turn the mushroom sauce to low. Stir a spoonful of warm sauce into the 150 g sour cream, then return that mixture to the pan with the last 1 g salt. This gradual mixing makes it easier to distribute the cool sour cream through the hot sauce. Do not bring the finished sauce to a hard boil.
Add the sliced beef and board juices for just 1–2 minutes of gentle warming. Divide mash between four bowls, spoon the stroganoff beside it and finish with scallions and parsley. Keeping the steak out during sauce reduction prevents it from becoming an unintended long-cooked ingredient while you wait for the gravy to thicken.
Common questions
Can I use stewing beef in the same cooking time?
No. This method is written for top sirloin cooked as a steak. Chuck or another stewing cut needs a different, longer cooking method to become tender.
Why has my sour-cream sauce become grainy?
Excessive heat after adding sour cream can split the sauce. Mix it with a spoonful of warm sauce first, return it over low heat and avoid boiling.
Technique & food-safety references
These primary references support the technique, safety and storage guidance. The recipe and cooking explanations are original Recipe Pinboard content.
