Thursday, April 25, 2013

Eggsperiment: Slow poached eggs (onsen tamago) in 5 minutes?

The other week I was waiting in line at the grocery store and I saw a copy of Cook's Illustrated sitting on display.  An article jumped out to me, titled "Perfect soft boiled eggs."  My curiosity was piqued so I hurried up and skimmed the article before it was my time to check out.  The biggest takeaway from the article was the use of steam to cook eggs to precise doneness - it was kind of a revelation to me, someone who has struggled with getting consistent results with hard boiled eggs.  Often, because I am scaling egg amounts, my hard boiled eggs are difficult to get quite right.  Adding different amounts of eggs to already-boiling water changes the temperature of the water significantly enough that your assumptions about cook temperature can no longer be trusted.  With steam, you know that you are always cooking at 212º (assuming you are relatively close to sea level blah blah) so whether you are cooking 1 egg or a dozen, the times are consistent and the results are predictable.  It's a fantastic knowledge tidbit to have tucked away, and a reminder of how great Cook's Illustrated can be when it is on form.  Thinking more about the concept of cooking with steam, I eventually settled on a question that I wanted to resolve:

I often cook slow poached eggs at home, could I use the steam technique to cook them at a fraction of the time?  

Slow poached eggs are also referred to as 60 minute eggs, or onsen tomago in Japan (onsen being natural hot springs, the story being that eggs are traditionally left by local residents in onsen and, upon being retrieved, are perfectly cooked).  Slow poach eggs are cooked in a water bath at a temperature of 145º for 45 minutes to an hour - resulting in a white that is just set (white but still runny) and a yolk that is beginning to thicken but not yet cooked (which would first begin to turn into a fudge-like consistency before hitting what we think of as hard-boiled).  Because the water never goes above 145º, the eggs are never done past where they should be.  The only downside to the water bath is that it takes a long time and requires a fair amount of planning in advance.  Here is a chart depicting the different doneness of eggs.  Notice that at 144º we are seeing whites turning white but very much still runny.  Also - tangent - it's fucking fascinating that 2 degrees of difference from  146º to 148º causes that much of a change in the yolks.  Eggs are amazing things.

(photo from

Cook's Illustrated recipe for soft boiled eggs was to place the eggs in a steamer for 6 minutes 30 seconds before immediately transferring to an ice bath.  I cut that to 6 minutes 10 seconds because I wanted the yolks to be even runnier (they began setting at 6:30) but otherwise it works like a charm.  I wondered if I could cut that cook time in order to just solidify the whites but not cook them to soft boiled, thus rendering me a soft poached egg.  I attempted to steam 2 eggs with times of 4 minutes and 5 minutes (I made an assumption that cooking time would follow an exponential curve, taking a while to heat up but then heating incredibly quickly after a few minutes).  My results were that the whites on the 4 minute eggs were still mostly clear and uncooked - completely unusable in their current form. The whites on the 5 minute egg were milky and still somewhat runny, and the yolk was thickened.

5 minute egg
It was a  good result, unfortunately I realized that one of my fears had come true.  Because I placed the eggs in a 212º heat source, the whites closest to the shell will always completely set (to a rubbery state).  I ran head on into the very reason that sous vide cookery exists - providing even cooking throughout a product through consistent temperature application.  You can't fake even heating, you can only work around it.  My plans were foiled and my question is answered - you cannot make a slow poached egg in 5 minutes using steam.  However, I would say that cutting Cook's Illustrated's times down did result in a totally usable egg.  For times when I don't want to wait 45 minutes but I want something resembling a slow poached egg, I will be more than happy to quickly steam one to get a similar result.  At least I found a perfectly suitable substitute.  Next time, I will attempt cutting 5 minutes down to perhaps 4:45 or so, to see if it creates noticeable differences in the amount of set whites.  I suspect that it will be difficult to find the precise point where eggs stop being clear and start being whites through steam-based heating though.

Makeshift oyakodon - leftover chicken karaage and tomagoyaki with the 5 minute egg

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