This is a very helpful and interesting article by The New York Times. Although it was written in 2008, i found it extrmely helpful and wanted to share some key snippets with you.
To read the full article go here
Importance of ageing the cookie dough
Given the opportunity to riff on his cookie-making strategies, Mr. Rubin revealed two crucial elements home cooks can immediately add to their arsenal of baking tricks. First, he said, he lets the dough rest for 36 hours before baking.
Asked why, he shrugged. “I don’t know,” he said. “They just taste better.”
“Oh, that Maury’s a sly one,” said Shirley O. Corriher, author of “CookWise” (William Morrow, 1997), a book about science in the kitchen. “What he’s doing is brilliant. He’s allowing the dough and other ingredients to fully soak up the liquid — in this case, the eggs — in order to get a drier and firmer dough, which bakes to a better consistency.”
A long hydration time is important because eggs, unlike, say, water, are gelatinous and slow-moving, she said. Making matters worse, the butter coats the flour, acting, she said, “like border patrol guards,” preventing the liquid from getting through to the dry ingredients. The extra time in the fridge dispatches that problem. Like the Warm Rule, hydration — from overnight, in Mr. Poussot’s case, to up to a few days for Mr. Torres — was a tactic shared by nearly every baker interviewed.
To put the technique to the test, one batch of the cookie dough recipe given here was allowed to rest in the refrigerator. After 12, 24, and 36 hours, a portion was baked, each time on the same sheet pan, lined with the same nonstick sheet in the same oven at the same temperature.
At 12 hours, the dough had become drier and the baked cookies had a pleasant, if not slightly pale, complexion. The 24-hour mark is where things started getting interesting. The cookies browned more evenly and looked like handsomer, more tanned older brothers of the younger batch. The biggest difference, though, was flavor. The second batch was richer, with more bass notes of caramel and hints of toffee.
Going the full distance seemed to have the greatest impact. At 36 hours, the dough was significantly drier than the 12-hour batch; it crumbled a bit when poked but held together well when shaped. These cookies baked up the most evenly and were a deeper shade of brown than their predecessors. Surprisingly, they had an even richer, more sophisticated taste, with stronger toffee hints and a definite brown sugar presence. At an informal tasting, made up of a panel of self-described chipper fanatics, these mature cookies won, hands down.
According to most of the bakers, only chocolate with at least 60 percent cacao content has the brio to transform the dough into the Hulk Hogan of cookies. Some, like Mr. Rubin and Mr. Torres, have their chocolate made exclusively for them. Others, including the Mercer sisters, use high-quality imported brands, like Callebaut or Valrhona, and shoot for a ratio of chocolate to dough of no less than 40 to 60.
Break apart a Torres cookie, and a curious thing happens. Inside aren’t chunks of chocolate, but rather thin, dark strata. “I use a couverture chocolate, because it melts beautifully,” he explained, something traditional chips don’t do. Couverture is a coating chocolate used, for instance, for covering truffles. To get his trademark layers, Mr. Torres has his chocolate, which is manufactured by the Belgium company Belcolade, made into quarter-size disks — easily five times the volume of a typical commercial chip. Because the disks are flat and melt superbly, the result, he said, is layers of chocolate and cookie in every bite.
“You can’t underestimate the importance of salt in sweet baked goods,” she said. Salt, in the dough and sprinkled on top, adds dimension that can lift even a plebian cookie. To make the point, she referred to her recipe for Sablés Korova, a chocolate chocolate-chip cookie with a hefty pinch of fleur de sel, from her book “Paris Sweets” (Broadway Books, 2002). Five years ago, sea salt as a must-have ingredient and garnish for sweets wouldn’t have registered on the radar of many home bakers, but now it has become almost commonplace, in part because of Ms. Greenspan’s unwavering belief in its virtue.