• Season the beef – Sprinkle the beef with salt and pepper.
• Brown the beef – Heat 1 tablespoon of the olive oil in a large, deep, heavy-based pan over medium–high heat. Brown the beef, in batches, for 2–3 minutes on each side, using the remaining oil as needed, until browned and golden. Set aside on a plate. 
• Deglaze the pan and add onion and garlic – To the same pan, add 60 ml (¼ cup) of water to scrape up all the sticky bits from the bottom. Once most of the water has evaporated, add the onion and garlic. Cook, stirring, for 2–3 minutes, or until the onion has softened.  
• Add the mushrooms – Add the mushrooms and cook for 2–3 minutes until softened. 
• Add the flour – Add the flour and stir continuously for 30 seconds, or until a lumpy paste forms around the onion and mushrooms.

If using a slow-cooker:

• Add the tomato paste, paprika, Worcestershire sauce and beef stock to the slow-cooker and stir to combine.
• Transfer the cooked beef and mushroom mixture into the slow-cooker and stir gently to combine. Don’t worry if the beef is not completely submerged – it will soften into the sauce as it cooks.
• Cook on high for 4 hours or on low for 8 hours. When cooked, the beef should easily pull apart with a fork. If not, continue to cook in 30-minute intervals until soft (if you would like to thicken the sauce, see note 2).
• Use a spoon to ladle roughly 250 ml (1 cup) of the sauce into a small bowl. Add the sour cream and mix well to combine. Return the sauce and sour cream mixture to the slow-cooker. Stir to combine (this method will stop the sauce from splitting and the sour cream from curdling). 

If using a pressure-cooker:

• Add the tomato paste, sweet paprika, Worcestershire sauce and beef stock to the pressure cooker insert. Stir to combine, then return the beef to the pot along with the mushroom mixture.
• Secure the lid and ensure the steam release is set to closed (or in the position for pressure cooking – refer to your manufacturer’s instructions). Cook on high pressure for 35 minutes.
• Allow the pressure to release naturally for 10 minutes, then manually release the remaining pressure, if needed. Check the beef – it should easily pull apart with a fork. If not, cook for an additional 5–10 minutes at high pressure.
• Use a spoon to ladle roughly 250 ml (1 cup) of the sauce into a small bowl. Add the sour cream and mix well to combine. Return the sauce and sour cream mixture to the pressure cooker and stir to combine (this prevents splitting/curdling).
• If you’d like the sauce thicker, set the cooker to Saute (or simmer) and reduce for 5–10 minutes, stirring occasionally, until thickened to your liking.

Or continue with stovetop method:

• Add the seasonings – Add the tomato paste, sweet paprika, Worcestershire sauce and beef stock. Stir to combine, then return the beef to the pan.
• Cook, covered – Return to the boil, then simmer on the lowest heat for 1½ hours, covered, stirring occasionally. If the sauce is sticking to the bottom of the pan, add 125 ml (½ cup) of water.
• Cook, uncovered – Remove the lid and cook for an additional 1 hour to thicken.
• When cooked, the beef should easily pull apart with a fork. If not, continue to cook in 15-minute intervals until soft. 
• Add the sour cream – Once the beef is soft and melting, use a spoon to ladle roughly 250 ml (1 cup) of the sauce into a small bowl. Add the sour cream and mix well to combine. Return the sauce and sour cream mixture to the pan. Stir to combine (this method will stop the sauce from splitting and the sour cream from curdling).
• Serve – Serve with pasta, rice, polenta or mashed potato, garnished with parsley, if using.