I’m writing this to clarify the post on medium-boiled eggs I wrote 3 years ago. This is because there have been a few emails from my readers in Thailand who wonder, if the 7-minute cooking time is indeed sufficient, why their eggs still turn out a bit runny. After going back and forth with those readers, I’ve discovered that, in every case, duck eggs are involved.
You see, duck eggs, due to their richness, are by far the preferred choice among the Thai people, especially when it comes to savory dishes or traditional Thai desserts. I happened to have large chicken eggs in mind when I wrote the original post, because the majority of my readers reside in the United States where duck eggs are hardly used. I should have included a remark on this issue in that post. I’m sorry I didn’t.
Let me make amend with this post then.
So to be clear: if you use large chicken eggs, cook them for 7 minutes (start counting at the time when the eggs go in); if you use large duck eggs, cook them for 8 minutes.
Those who live in Thailand are already familiar with the concept of khai tom yang ma-tum which refers to eggs that are boiled to the point where the whites are tender and the yolks have the consistency that is likened to the gummy sap of bael (ma-tum). That is to say that the consistency of the yolk is somewhere between that of soft-boiled eggs with yolks runny enough for you to dip soldiers in and hard-boiled eggs with solid, opaque, chalky yolks.
If you look closely at the photos right above this paragraph, you will see that the yolks of the “bael-sap eggs” in the top photo (with rice noodles) are runnier than those of the eggs you see in the bottom photo showing a typical rice-curry shop (where these eggs are served both as a side and a full-fledged main). The egg yolks in the bottom photo are somewhat firmer around the edges whereas the centers are still a bit runny. What you see in both photos all count as bona fide bael-sap eggs.
I personally like my yolks a little runny like what you see in the original post. This is not to say that there’s anything wrong with the kind of bael-sap eggs with firmer yolks. People like different things.
The key, though, is that even though runny, the yolk still has to be thicker than that of a soft-boiled egg. A test: halve one lengthwise and hold one half, cut side down, in mid-air, and you will see that the yolk of a soft-boiled egg will drip (also the white will be so soft that it can barely keep its shape) whereas the yolk of the runny medium-boiled egg will not.
Oh, and, as instructed, stir your eggs around a few times while they’re cooking so the yolks stay in the center. Not only does this make your medium-boiled eggs look more pleasant when you serve them halved but it also prevents what you see in the photo at the very top: the yolks are way too close to one side making it difficult to peel the whole eggs without breaking them open.
[Added September 24th, 2013: One of my readers, Vanessa Kimmel, shared with me a trick her mother had taught her: The morning before she boils the eggs, she turns the carton upside down and leaves it there for an hour or two; this allows the yolks to center themselves. It works every time, she says. Thanks, Vanessa!]