Place flour, paprika, salt & pepper in bowl. Working in batches, coat beef strips in mix. Dust off excess
Heat a large frying pan over medium high heat. Add tablespoon of oil. Cook beef in batches until well browned. Remove to a bowl and set aside.
Return pan to medium heat. Add a little more oil. Sauté onions for 2-3 minutes until starting to soften then add mushrooms. Cook for another 5 minutes until mushrooms are golden. Stir in garlic. Cook for a minute, add tomato paste, stock and Worcestershire sauce and bring to the boil. Reduce heat and simmer for 3-4 minutes. Return beef strips to the pan.
Remove pan from heat, stir through sour cream and parsley, until fully combined. Cook gently for a minute until heated through. Serve with pasta or rice.