Scenario: I want to hard-boil a single whole egg with the least amount of effort and active cooking time. I don't own an egg steamer and don't want to buy another kitchen gadget that takes up space without being used most of the time. I also don't want to cook the egg in a pot of boiling water because it seems wasteful to heat up so much water for a single egg. (Edit: I only have 2 sizes of stove hobs, so the smallest pot I own is the size of the smallest hob: 14,5 cm / 5.7 inch diameter)
However, I do have a thermos flask with 1 liter capacity and an opening big enough to put an egg inside. Yesterday I put an egg in and filled it with about half a liter of freshly boiling water. After 25 minutes only a few millimeters of the outer eggwhite were cooked and the inside was completely liquid. I took the egg directly from the fridge, so that might have contributed to the fail.
I also thought about putting the egg directly into my electric kettle, but if the shell cracks it would be a nightmare to clean the kettle afterwards.
I know that microwaving an egg has an insanely high risk of the thing exploding in your face. There are many reports of people receiving really bad burns to their faces and hands.
Is it even possible to cook an egg in a thermos flask? Is there maybe another method I overlooked? I'm willing to wait about an hour for the egg to finish cooking, as long as I don't have to actively monitor the process.
I tried again with the 2 methods that appealed to me the most:
Joe M's method: egg in thermos flask. I only have the "keep things warmer for a little longer" kind of flask, not the "keep things hot for hours" vacuum kind, but if I fill it up to the brim with boiling water and gently tilt it every 5 minutes to even out the temperature insite, I can get a hard-boiled egg in 20 minutes.
Tjaden Hess' method: steaming in a pot. This works like magic. I made a little "throne" for the egg from aluminium foil and boiled a cup of water in the electric kettle before pouring it into the pot, which was heating up in the meantime. After pouring the water and adding the lid, I could turn the hob down to the lowest setting and forget about the egg for 10 minutes. It came out perfect and this method required the least effort and resources by far.