Fill coffee mug half of the way up with cold tap water.
Put a splash of vinegar into the water (about a tablespoon or so).
Crack an egg into the water.
Microwave for one minute (feel free to adjust the length of time, depending on your microwave and your personal preferences for egg runniness). Important Safety Note: You may want to drape a paper towel over the cup in case the egg explodes, especially if you don’t yet know the exact length of time that works best with your microwave!
Remove from microwave and use a spoon to place the egg on a plate (or toast/muffin/whatever).
Season egg to taste (I personally love salt, pepper, bacon bits, and cheese, but you could also do hollandaise, for example).
Update – I wanted to find out exactly at what point the eggs could potentially explode when using this technique, so I did some more experiments with more eggs and here is what I found. I have a 1200 watt microwave oven, so keep that in mind:
The first egg I cooked exploded after 1 minute and 16 seconds:
With the second egg, I tried something different and pierced the yolk with the sharp point of a knife. This time, it cooked for 1 minute and 25 seconds before exploding.
I was curious what would happen if I reduced the power, so I lowered the power to 50% (600 watts) and tried again with a third egg. This time, the egg got all the way to 3 minutes and 24 seconds, but when it exploded it seemed to do it with a lot more force than the prior two times.
I decided to see if cooking the egg at half power would give me more control over the results, and sure enough, it did!
I cooked another egg at half power for 2 minutes and I got a poached egg that was still quite runny:
I tried it again at half power, but this time for 3 minutes. This time the egg was clearly over-cooked, and it actually exploded when I cut into it:
I split the difference and tried again, this time at half power for 2 minutes and 30 seconds. This gave me a poached egg that was almost identical to the egg I had cooked earlier at full power for 1 minute (although it was cooked a bit more evenly):
Each time I did an exploding egg experiment, I draped a paper towel over the cup, and after the experiment I reset everything, cleaning and drying the microwave and cup and cooling everything back down to room temperature.
So the guess the lesson is:
Experiment with your own microwave to find the best times that work for you, and make sure you drape a paper towel over the cup, just in case!
Also, if you poach the egg so it is well done, it is probably best to let the egg sit for a minute after cooking it, so it won’t explode when you cut it open.