Published January 1, 2013. From Cook's Illustrated.
The usual approach is hit or miss. We cooked more than 1,000 eggs to develop a truly reliable method that delivers a tender, set white and a fluid yolk every time.
Soft-cooked eggs are a bit of a crapshoot because you can’t rely on any visual cues to monitor the eggs’ progress. You don’t know if you’ve succeeded or failed until you’re already seated at the breakfast table.
We wanted a method that would produce consistent results for any cook, in any kitchen, using any equipment, whether he or she was cooking one egg, four eggs, or even a half-dozen.
The two components of an egg—the white and the yolk—react very differently to heat. Most important: The white and the yolk begin to solidify at very different temperatures. This means that when cooking an egg that we want to be ultimately both solid (the white) and liquid (the yolk) at once, we have to carefully bring the whites up to a much higher temperature.
We found that we could get perfectly soft-cooked eggs by adding two eggs to boiling water and then removing them after several minutes. But when we tried adding extra eggs, the whites didn’t cook through. That’s because adding the cold eggs to the saucepan temporarily lowered the temperature of the water. With more eggs, the water’s temperature dipped lower and took longer to return to 212 degrees.
We needed to use boiling water to cook the eggs without actually submerging them in it. What about steaming? Using a steamer basket worked perfectly—and it turned out that eggs cooked in steam took exactly the same amount of time as eggs that were submerged in an ample amount of boiling water. With that in mind, we made our method even easier by losing the steamer basket but keeping the small quantity of water. Because of the curved exterior of the eggs, they didn’t make enough contact with the water to lower the temperature significantly, so we got beautiful tender yet fully set whites cradling warm, fluid yolks just like we had gotten in the steamer.list of recipes