Heat one tbsp of the oil and butter in a large frying pan (skillet) over a medium-high heat, until the butter starts to foam.
Add the onion, and cook for 5 minutes, stirring often, until the onion starts to soften.
Add the mushrooms and cook for a further 3-4 minutes, stirring often, until lightly browned.
Transfer the contents of the pan to a bowl. Place the pan back over the heat and turn the heat up to high.
Drizzle the strips of steak with the remaining 1 tbsp of oil and sprinkle on the salt and pepper.
Place the steak in the pan in a single layer and cook for 1 minute, then turn the steak strips over and cook for a further 30 seconds.
Add the onions and mushrooms back to the pan and turn the pan down a medium heat.
Pour in the double (heavy) cream, followed by the sour cream. Stir and slowly heat through until the sauce is hot and the sauce at the edge of the pan is just starting to bubble slightly (don't let it boil). Turn off the heat.
Spoon the stroganoff over cooked rice or pasta and sprinkle on the paprika before serving.
Best cut of steak for beef stroganoff:
Ribeye,sirloin or fillet steak are best. You’re looking for a steak with lots of flavour, that can be cooked quickly over a high heat without becoming chewy.
Can I make it ahead and/or freeze it?
I always like to try to include make ahead and/or freezing instructions where possible, but this one just doesn't taste as good if made ahead. You lose all the juiciness and tenderness of the steak, and it's just too much of a shame to reheat a nice piece of ribeye. So my advice is to make it right before serving. Now, if you wanted to prep ahead, you could slice the onions, mushrooms and steak (cover and refrigerate). You could even cook the pasta or rice. I often make rice ahead and re-heat in the microwave. For pasta, I just cook it for 2 minutes less than the pack instructions, then drain, run under cold water, drain again and store, covered, in the fridge. You can pop it in a pan of boiling water for 2-3 minutes to finish off the cooking process right before serving.
A note on the fat content of cream:
I wouldn’t recommend using low fat cream. Any cream under 25% fat will curdle when heated. Whipping cream is an ok replacement for double cream (approx. 35% fat, compared to double/heavy which is approx. 48% fat), but don’t use single cream.Full fat sour cream shouldn’t be replaced with lower fat sour cream. Full fat sour cream is about 20% fat – which is under that 25% fat threshold. The higher fat in the double/heavy cream that we add in first helps to protect the sour cream, so long as it’s heated slowly and not boiled.Ultimately, this is an indulgent dish, so it will be high in fat – but is also delicious and filling.Nutritional information is per serving, not including rice or pasta.