1 tablespoon shredded flat-leaf parsley leaves, extra to serve
Season the steaks with salt and pepper.
Heat the olive oil and 20g butter in a large frypan over medium-high heat. When sizzling, add the steaks to the pan. Cook steaks for 3 minutes each side for medium-rare or until cooked to your liking. Transfer to a plate, loosely cover with foil and rest while making the sauce.
To make the stroganoff sauce, return the frying pan to medium heat and add 25g butter. When melted, add mushrooms and the garlic and cook for 4 minutes, stirring, or until the mushrooms have softened. Add the brandy and cook for a further 1 minute or until most of the liquid has evaporated. Add the beef stock, thickened cream and Fountain Mustard Sauce. Reduce heat to low and simmer for 10 minutes until the sauce has reduced and thickened slightly. Remove from the heat and stir in the parsley.
Divide the steaks among 4 plates, ladle over the stroganoff sauce and serve potatoes, salad leaves and extra Fountain Mustard Sauce if desired.