I have for some time been interested in sous vide, cooking in a vacuum sealed bag and wandering if I could use the basic principles with a thermal cooker. I therefore bought myself a vacuum packaging unit and some bags suitable for cooking in. The principles of sous vide is to place a vacuum sealed bag containing the food into a bath of water. The water is kept at a constant temperature. This will eventually cook the food when the centre of the food is at the same temperature as the water.
In the case of beef this may be as low as 52ºC if you want your beef rare. The water is therefore held at that temperature for as long as 48 hours while the meat heats through. What you are aiming at is the same temperature on the outside of the meat as that of the canter.
If we compare sous vide cooking to using a conventional oven we still need the centre of the meat to be 52ºC if we want it rare but while it is reaching that the outside will be getting overcooked due to the higher heat required to cook in air.
In a thermal cooker I realise that we can’t keep the water at a fixed temperature but as the maximum temperature we can achieve is only 100ºC (the boiling point of water) the outside will not be overcooked as it could so easily be in the oven.
With this in mind around midday today I prepared a half leg of lamb by putting thin slivers of garlic in slits in the skin. Next I sprinkled a mixture of sea salt, freshly ground black pepper and lavender flowers (which work so well with lamb) all over the meat. I then put the lamb in a bag and vacuum sealed it before placing it into the inner pot of the thermal cooker. Having filled the pot with cold water I brought it to the boil and then turned down the heat and simmered for about 10 minutes with its lid on before place the inner pot into the insulated outer container.
After shutting the lid of the outer container I left the lamb to thermal cook without power for 8 hours at which time the temperature was still 67°C.
Having carefully removed the bag from the water as it was still hot I slit the bag and poured the meat juices into a jug before removing the lamb.
After patting the lamb dry I decided to give the skin some colour by heating a frying pan with a little oil and placing the joint in skin side down.
As you can see the result is a lovely joint of lamb that tastes amazing.
You may want to experiment with different thermal cooking times especially if you want it a bit rarer.
This system can be adapted to any meat and whether you brown the outside is up to you.