You've mastered the vacuum sealer, you've got to grips with the water bath and now you're looking to step things up a gear. The first rule, and perhaps the most important thing to get your head round when graduating to an intermediate level in sous vide, is: there aren't any rules.
Ok, there are some rules. You shouldn't cook a salmon fillet for more than 30 minutes, and you shouldn't cook beef cheeks for less than 8 hours. But, unlike patisserie or baking, there is no need to be held to strict guidelines when it comes to sous vide; cooks will be rewarded for being adventurous and veering off-piste. Because, when you're tinkering with water temperature and cooking times, it turns out that there are many, many different ways to boil an egg or cook a fillet of steak to pinkish perfection.
Traditionalists may mourn the demise of the bouncy, hard white of a boiled egg, but you only have to look as far as Adam Simmonds’ slow-cooked duck egg with duck confit, asparagus and cobnuts to see how much a slow-cooked egg can enhance a dish. Sous vide expert Douglas E. Baldwin describes the "perfect" egg as having 'a custardy texture'.
To create the sous vide showstopper of the slow-cooked egg, Baldwin suggests you set the water bath at 64.5°C, and cook an egg in its shell for 45-60 minutes. Crack it onto a slotted spoon, so the white drains away and you're left with a rich, custardy yolk.
As is typical of the variation that creeps into recipes though, chef Simmonds’ instructions are very different to Baldwin's. He advises: 'Preheat the water bath to 60°C. Place the duck eggs in the water bath for 1 hour, then reduce the temperature and hold them at 50°C.'
Experiment with times and temperatures to create different effects. But remember that 54.4°C is classified as ‘raw’ - one and a quarter hours of cooking at 57°C will pasteurise the eggs and turn the whites milky.
Cooking fish sous vide is exciting for a whole host of reasons. Firstly, chefs can exert more control over the precise temperature the fish is cooked at, in a way that they can't if, for example, sautéing a thin fillet in a blindingly hot pan. This suits the delicate texture of fish, and is particularly exciting for preparing seafood like lobster or octopus, which has a tendency to turn rubbery if not cooked properly.
Secondly, sous vide intensifies the flavour of a fillet of white fish - a flavour which is easily overwhelmed or diluted when poached, as the flavour leeches into the cooking juices. Finally, fish is relatively quick to sous vide, so you can easily decide to sous vide fish on your way back from work, rather than having to have planned it before breakfast.
There are a few simple rules with fish. The first thing to remember is that it's rare that you will pasteurise fish when cooking it sous vide, so make sure that you forewarn diners with a weak immune system, or only use sushi-grade fish. No matter how strong your constitution, it's important to only use the freshest of fish for this same reason. To pasteurise fish, it needs to spend 2.5 hours at 55°C (see Douglas Baldwin's table for more information). Such lengthy cooking time compromises too much on taste and texture, so it's best to assume that fish cooked sous vide will be unpasteurised, and to take the appropriate precautions.
The standard guidelines to cooking fish sous vide are as follows:
42°C (108°F) rare
50°C (122°F) medium rare
60°C (140°F) medium
As ever, these are only guidelines. Paul Foster (only just!) cooks a thin salmon fillet at 40°C for 10 minutes; Chris Horridge cooks monkfish tail at 40°C for 15 minutes; and Nigel Mendham cooks his cured pollock at 54°C for 14 minutes.
When considering how long to cook fish, it's important to remember that the thickness of the fillet will impact timings, as will the type of fish – a lean fish cooks far faster than a fatty or oily fish. But somewhere between 10-30 minutes is most conventional.
Don't be afraid of sealing fish in the vacuum bag with additional flavourings. But be sparing – a small pinch of paprika, a sprig of lemon thyme or grating of lime zest all go a long way. Remember that garlic and onions have a tendency to take on a bad flavour during sous vide cooking.
The final tip concerns the visually unappealing, milky-white protein which can appear across the surface of fish when it is being cooked sous vide. An easy way to prevent the albumin from forming is to brine the fillets in a 10% salt solution for 10 minutes in the fridge. Afterwards, rinse the fillets, pat them dry, and then cook as usual.
Regardless of what type of meat you are using, or what cut you are cooking with, there are a few basic tips which should be followed, and a very loose temperature guide, below.
50°C (125°F) rare
55°C (130°F) medium rare
60°C (140°F) medium
70°C (160°F)+ well done
"In general, the tenderness of meat increases from 50°C to 65°C, but then decreases up to 80°C," says Douglas E Baldwin. Despite most sous vide cooking falling within this 15-30°C window, cooking times vary wildly, dependent on whether you're cooking a portion of beef fillet (20 minutes) or slow-braising feather blade beef (60 hours).
The thickness, size and shape of the meat you are cooking will impact greatly on the temperature you should use and the length of time you cook it for. The best way to cook meat sous vide is to find out what internal temperature will give the desired results (e.g. 50°C for a rare finish) and cook the meat for as long as it takes to reach that temperature - this is what makes it so difficult to overcook meat using a sous vide system. Obviously, it will take a thicker cut of meat longer for that temperature to be reached at its core, but once it has, it can be held at that temperature without overcooking.
Some cooks sing the praises of cooking chicken breast sous vide: after 2-3 hours at 65°C a chicken breast will be slightly pink and moist, but safe for consumption as it has been pasteurised during the slow cooking. Others talk about the transformative nature of braising: the meat can be brought up to the exact temperature that tissues melt into gelatine, but no higher. Other cooks exalt the effects of sous vide when cooking a butterflied leg of lamb: it cooks the meat uniformly all the way through, creating the most perfect medium-rare cross section.
The Maillard Reaction
It doesn't matter whether you use a 200°C skillet, a whacked-up grill, Salamander or a blowtorch – to achieve meaty, roasted flavours, chefs need to finish a piece of sous vide meat by browning the outside. The Malliard Reaction, which creates these distinct flavours, doesn't occur until the surface of the food hits at least 150°C. So once you've finished cooking the meat in a water bath, it will need a final blast to crisp up the skin and create a flavoursome exterior. Whatever method you employ, make sure it's very hot, so the meat is quickly 'seared', not 'cooked'.