Why does it make a difference to refrigerate the dough? (sometimes up to 3 days!)
"Ripening is just a fancy term for resting cookie dough in the fridge before baking it. Some recipes call for a quick chilling, while others recommend up to 72 hours of resting before baking them. This resting time does two crucial things for cookies.
First, it allows the fat in the cookies to chill and firm up. Recipes that call for chilling often contain a high percentage of fat; this is because cold fat melts slower while baking, preventing your cookies from spreading too thin.
Second, and more importantly, the resting time allows the flour to fully hydrate and soak up the liquids in the dough. Unlike other baked goods, cookie dough is relatively dry and the bulk of the liquid content comes from the eggs — and because eggs are so thick, it takes time for the flour to absorb them. A long hydration time solves this issue and gives the flour time to fully hydrate so the dough is completely moistened. Similar to the autolyse method in bread baking (where you allow the flour and water to sit undisturbed), it’s all about fully hydrating the flour. This results in cookies that brown better, bake more evenly, and have a slightly more complex flavor."
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