AKA “hay box cooking” or “thermal cooking”

A chance remark made me wonder about the possibility of using an insulated container to conserve the heat in a cooking pot after initial heating on a conventional hob. A few experiments showed that perfectly nice meals could be produced using far less energy than would be required to cook them in the oven or on the hob.

The first experiment was butternut squash risotto cooked in a saucepan placed inside a wooden box and packed around with chunks of expanded polystyrene and strips of fibrous pipe lagging. In fact, leaving it to cook for two hours was a little too long as the rice was slightly too soft, but it was an encouraging start anyway.

After that, we bought a camping saucepan to get round the difficulty of packing insulation around a saucepan handle. With the new pan – once again in the wooden box with polystyrene packing - I cooked up some aubergines with lentils and tomato. This was left cooking for 2.5 hours, which was fine, although the lentils could have been a little softer.

Having proved to our satisfaction that stored heat cooking was a runner, we bought a 24 litre coolbox, added extra insulation in the form of foil backed insulation and made a cloth sack to keep everything in place around the hot cooking pot.

Photos - Stored heat cooking – 2010-09

We've now tried various recipes but it's mostly a case of cooking what we have in the fridge, the store cupboard or the garden. We've even fed the results to other people without ill effects. 

Examples :


Butternut squash risotto

(adapted from pumpkin risotto recipe on www.thermalcookware.com.au )
3 cups of hot vegetable stock (500-600ml)
1 tablespoon of olive oil
1 medium onion, chopped
1 clove of garlic, finely chopped
1 cup of risotto (arborio) rice (200-220 gram)
1/4 of a cup of dry white wine (optional) (200 ml approx)
salt and pepper to taste
1 tablespoon of butter
grated parmesam cheese (optional)
half a butternut squash chopped into small chunks
1 cup of baby spinach leaves (optional)
toasted pine nuts (½ cup)


Heat the oil, add the onions, garlic and cook for a few minutes.
When softened add the rice and toss through for a minute.
Add the wine and stir for a minute allowing some evaporation.
Add the stock and butternut squash and bring the mixture to the boil.
Simmer for 1 minute with the lid on.
Transfer the thermal cooker
Leave for a minimum of 1 hour (1 ¾ hours about right)
Stir in the butter, baby spinach leaves and parmesan cheese.
Allow to sit for 10 minutes before serving.
Sprinkle each helping with the toasted pine nuts.

Lentil Stew
These are the exact quantities, method and timing used on one occasion, but normally I just use whatever ingredients I have in stock and in quantities that seem about right. The timing is also very vague. Experimentation will reveal ingredients that need more time. So far, we haven't had anything under-cooked and the cooking pot is still remarkably hot even after 3 hours.
Main ingredients
150gr red split lentils - rinsed
150gr new potatoes - (10 small ones)
70gr carrots (5 small ones)  cut longwise
110gr shallots (4) - chopped in quarters
70gr green beans - cut in 4
90gr broccoli (5 florets)
2 tabs olive oil
Other veg or pulses would do or meat if suitable for slow cooking
1 veg stock cube in 500ml boiling water
1 tab sun dried tomato in olive oil
or whatever seasoning you like
Cook shallots in olive oil for approx 4 minutes
Add carrots and potatoes and cook for 2 more minutes
Add lentils and stir in for about 1 minute
Add beans and broccoli, stock liquid and seasoning and bring to a fast boil for a couple of minutes.
Slow cooking
Transfer cooking pot to insulated container (fairly quickly to avoid cooling)
Leave until you want to eat it - in this case 2 hours 50 minutes. Everything was well cooked but 2 hours 30 minutes would probably have been sufficient.


Stored heat cooking