Cooking in a Thermos or vacuum flask. Leek and potato soup recipe
Posted on Oct 29, 2011 in Kitchen equipment, Save Money | 18 comments
The raw ingredients
When I first heard about cooking in a vacuum flask I had an image of a whiskery maiden aunts filling vacuum flasks with Spam, gravy granules and boiling water.
Why on earth would I want to cook in a Thermos?
The idea seemed grim until I bought my 1920’s Thermos at the village fete one year. This is a marvellous piece of kit. It was crying out to be used so I started researching the possibilities and I’ve used it for slow cooking ever since.
During WW2 vacuum flask cooking was normal. Apart from a few minutes coming to boil on the hob and a kettle of boiling water, it uses no energy. Like slow cooking and now, halogen cooking, seals in and enhances the flavours. So why not use cutting edge technology that was developed at the start of the last century to cut your energy bills and produce great food?
Last Sunday we were thrilled to be included in an article by Sarah Lonsdale on frugal cooking. This appeared in The Sunday Telegraph. It featured our 1929 Thermos – which has a capacity of 4.8 litres.
This got us thinking. Wouldn’t it be fun to develop a series of recipes for vacuum flask cooking. As most people don’t have access to a 4.8 litre flask we decided to invest in a good 1 litre flask. A flask that would keep water and food hot for 24 hours. The Thermos brand claims that its flasks keep food and water hot for 8 hours. Even though we are not planning to produce recipes that take over 8 hours to cook, the 24 hour flask is a good option as the heat would be more consistently retained over 8 hours. The Pioneer Vacuum Flask
The only other piece of equipment that we reckon is essential is a preserving funnel, which avoids dangerous splashes when filling the flask with hot food. The Pioneer flask doesn’t have a wide mouth.
I suspect that if you wanted to try this recipe in a Thermos, simmering the food for a further 5 minutes before putting it into the preheated flask would probably work. I’d love to hear how it turns out if you experiment.
Leek and potato soup cooked in a vacuum flask recipe
Equipment: 1 1 litre thermos (that holds heat for 24 hours) 1 preserving funnel
Ingredients:
1 leek (250g) washed well and sliced very fine
1 small onion (80g) peeled and sliced very fine
1 medium potato (150g) peeled and sliced fine
2 chicken stock cubes
Method:
Prepare all the ingredients and put then in the vacuum flask, pressing them down with the handle of a wooden spoon if necessary. Top up with water and pour the contents of the flask into a saucepan.
Fill the flask with boiling water, screw the top on firmly and leave for ten minutes – this will preheat the flask.
After ten minutes bring the saucepan of water and vegetables up to boiling point, empty the water from the flask and using the preserving funnel tip the contents from the saucepan into the flask.
Fit the top and the cup on the flask and leave for two hours.
Serve the soup with a little cream and hot crusty bread.
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Can you do meat as well as veg this way?
Hi The Liquineer
Yes you can do meat. That’s why we chose a vacuum flask with a very low heat loss. Chicken soup next and then we are going to try stew.
Well done on the article. I remember reading about when you found the thermos at the fete. Great photo too! Hope you and Danny are well.All the best, Kg.
Hi Kooky Girl
We are both up and running ATM. Hope that you are all well too!
We’re excited about these recipes. If we can cook delicious meals for a minimal energy outlay it can only be a good thing.
Great idea, I’ll see what my camping shop has in the way of a Thermos.
I’ve cooked oatmeal overnight that way, which worked pretty well, actually. This is a great idea, Fiona!
We recently purchased Stanley flasks, which I think are a bit pricier but worth it because one fell out of the car and didn’t break. All other vacuum flasks broke on us. The Stanley flasks are steel shells – no glass to break. Must try out the flasks though for cooking.
Now that is a great idea – I’m impressed that a small flask can keep the heat in for so long. We don’t have room in our kitchen for a slow cooker but I’m sure a flask will squeeze in a cupboard somewhere.
I have been cooking all my soups, curries and chillis in a flask for the past few months and thoroughly recommend it.
I have also been cooking similar foods in a big stainless steel stock pot. Once the food has come up to boiling point and simmered for five minutes, I turn the heat off and cover the pan in layers of towels, oven gloves etc and leave for a few hours.
The vegetables are cooked but do not stay as hot as in the flasks so have to be warmed up when ready to serve.
ooohhh! Never even thought of that! I have 2 small wide necked Stanley flasks which are brilliant for keeping soups/ stews and the humble coffee piping hot for hours. Just read the Sunday Telegraph article, makes me so wish I was better at these things. Has anyone tried the Mr D’s® Thermal Cooker they mention in the article.. Am intrigued! I have a slow cooker but am paranoid about leaving it switched on all day and evening as am normally out the house early and not back til 7ish. I may have to try and make a hay box….*goes off to look for my WWII cookbook which tells me how to make one…*
What a great idea! A friend of mine has a haybox cooker and I’ve been thinking about making one, but a portable flask version would be excellent and space-saving. I’ll try out some stews.
Check out this site,I use mine all the time.More expensive than a thermos but more or less indestructable.Have made bread and cakes in it too.
http://mrdskitchen.blogspot.com/search/label/THERMAL COOKING RECIPES
hi, Mr D’s thermal cooker and also his cake/bread making thermal cooker were reviewed recently in ‘Permaculture’ magazine, I think the cake/bread thermal cooker is in this edition and the thermal cooker in the previous, but they may be on the Permaculture website too. I think they seemed impressed by it, not cheap though.
What a great photo and write-up. Well done Fiona!
Fiona, thanks so much for the thermos cooking tip – our kitchen is being redone so I have no cooker except a camping gas burner at the moment and so far have done lamb stew and shin of beef in the thermos – the lamb was good and done the same day, the beef actually took two days (reheated and re – thermosed after day 1) but we ate it tonight and it was excellent. I forsee a lot of thermos cooking over the next few months, started after breakfast and eaten in the evening when the out door work is done…
Yogurt is another no brainer for a thermos flask – and a huge money saver – not to mention not needing yet another piece of kitchen equipment to clutter up the house.
Hi,
It was my thermal cooker that was mentioned in the article. We are just a small family company of myself and my wife and have been selling thermal cookers for around 5 years. If I can be of any help (even if you do not want to buy one) I am always very happy to talk thermal cooking. In 2009 I published a cookbook on thermal cooking and you will find a lot of recipes on my site. One thing you will find is the length of time that you can keep the temperature about 60C is dependent on the volume of the cooker. The 4.5L we sell will drop below 60C after about 7 to 8 hours whereas the 3L version we sell lasts around 5 to 6 hours.
If you do want to talk thermal cooking my number is 023 8084 7834. All the best Mr D