Creamy Mushroom Sauce for Steak

Porterhouse and scotch fillet are the two steaks that suit a creamy sauce best. Porterhouse has a firm, fine grain and a strip of fat that renders into the pan, while scotch fillet steaks are more marbled and stay juicy even if they go a touch past medium rare. Grass-fed steaks are leaner than grain-fed and cook a little faster, so start checking the temperature early, and allow about 1/4 cup of sauce per steak. For a mushroom sauce without cream, follow the recipe to the end of step 5, then add another 1/2 cup (125ml) beef stock and simmer until reduced by half. Whisk in 1 tsp cornflour mixed with 1 tbsp cold water and bubble for 1 minute until glossy. Take the pan off the heat and swirl in 20g cold butter and a dash of Worcestershire sauce. The result is closer to a rich mushroom gravy, and a good choice when you want something lighter. Swiss brown mushrooms give the deepest flavour and hold their shape, button mushrooms make a milder, paler sauce, and field mushrooms add an earthy richness but turn the sauce a darker grey-brown. All mushrooms are mostly water and shrink to roughly half their raw volume in the pan, so 300g looks like a lot at first. Spread them in a single layer and leave them alone before stirring, or they steam and turn grey instead of browning. A sauce that splits has usually boiled too hard. Take it off the heat and whisk in a splash of cold cream until it comes back together. Thickened cream is more forgiving than pure cream because it contains a stabiliser. If the sauce is too thin, simmer it for another minute or two, and if it is too thick, loosen it with a splash of stock. To make it ahead, cook the sauce in a frying pan, cool it quickly and keep it covered in the fridge for up to 2 days, then reheat gently with a splash of stock and stir in the steak's resting juices just before serving. Doneness guide for the steak after resting: rare 55 to 60C, medium rare 60 to 63C, medium 65 to 70C, well done 75C. Pull the steaks 3 to 5C below your target, then rest the meat while the sauce cooks. The Food Safety Information Council recommends cooking whole cuts of beef to at least 63C and resting them for 3 minutes. Rarer beef is a personal choice that pregnant women, older people, young children and anyone with a weakened immune system are safest avoiding, so cook their steaks to at least 63C.