Firstly, chop onion in half and cut about 3mm thick half round slices.Then chop garlic finely and slice mushrooms as well.With the fillet steak, cut into strips of about 5mm thick. Turn stove on medium, using a frying pan add 2 tbsp oil (I just use one pan to save on washing up) sweat off onions and garlic adding the mushrooms when they start to go soft. Then you are ready to add the paprika, stir quite well as to combine the paprika properly so they cover the onions, garlic and mushrooms.Taste at this stage to see if they have enough flavour and they are soft enough, then remove from pan into a bowl. Next turn the heat up to high put the other tbsp of oil in the pan flash fry the steak to seal it, (cook quickly as to stop the meat from boiling preventing the meat from overcooking) after about 2 mins add the bowl of onions, garlic and mushrooms back in and add the sour cream and stir to combine properly.Season to taste and serve with whatever you prefer, (my preference is french fries) the texture is lovely with the stroganoff.