Sprinkle the beef with the salt and pepper.

Using 1 tablespoon of the oil, brown the beef in a large heavy-based frying pan over medium–high heat for 8–12 minutes. Transfer to a plate and set aside.

Using the remaining 1 tablespoon of oil, cook the onion and garlic in the same pan over medium heat until softened, 2–3 minutes.

Add the mushrooms and cook for 2–3 minutes until softened.

Add the flour, stirring continuously for 30 seconds.

Add the tomato paste, sweet paprika, Worcestershire sauce, Dijon mustard and beef stock.

Return the beef and any juices back into the pan.

Return to a rapid simmer, then simmer over medium–low heat, covered, for 1 hour 30 minutes, stirring occasionally.

Uncover and cook for an additional 1 hour to thicken.

Once the beef is tender, stir through the sour cream to create a thick, creamy sauce. Set aside to cool.

Place the peeled, quartered potatoes in a large pot and add water to cover them.

Bring to the boil and simmer for 15–20 minutes or until the potatoes are soft enough to pierce with a fork.

Drain the potatoes and place them back in the pot. Allow them to steam-dry for 1–2 minutes.

Mash the potatoes with a potato masher, add the butter, milk and salt, and continue mashing until creamy.

Preheat the oven to 200°C (400°F).

Transfer the beef stroganoff mixture to a baking dish.

Spoon the mashed potato on top of the beef mixture, using a fork to rough up the surface.

Spray with olive oil and sprinkle with parmesan. Bake for 30 minutes or until the topping is golden and crispy.