Heat a tablespoon of the oil over a low/medium heat and cook the mushrooms and onions for 5 minutes until soft.
Put the onion and mushroom mixture in a large bow with the rest of the stuffing ingredients and mix.
Divide the mixture into 4 sausage shapes, the same width of the beef.
Lay the beef slices on a chopping board and place the stuffing at one of the short ends then roll up the beef.
Repeat with the remaining slices then use kitchen string to tie into a parcel.
Heat the remaining oil and fry the onions for 5 minutes until softened then transfer to a small oven dish.
Increase the heat, season the meat and sear on all side then place them on top of the onions.
Make the sauce by heating the butter until frothy then stirring in the flour for 1 minute.
Next, gradually stir in the stock and bring to the boil until thickened.
Pour the brown sauce over the beef, cover the dish with foil and bake at 170C/325F/150 FAN/Gas 3 for 40-60 minutes
Notes
Disclaimer:The nutritional information provided is approximate and is calculated using online tools. Information can vary depending on various factors, but we have endeavoured to be as accurate as possible.