Science you didn’t know you were doing
In a time-lapse video, it looks like a monster coming alive. For a moment, it sits there innocuously. Then it pulsates. Ripples move across its surface. It begins to bulge outwards, bursting with weird boils. In mere seconds, it triples in volume, its color darkens ominously, and its surface hardens into an alien topography of peaks and craters. Then, the kitchen timer dings. Your cookie is ready.
What happened inside that oven?
Don’t let the sugar and spice deceive you, for the baker is a mad scientist. In an act of aproned alchemy, she uses her oven to transform one substance into another. As her sugary creation heats up, the chemical compounds in the dough undergo a series of reactions that change them into different ones.
When the dough reaches 92° Fahrenheit, the butter melts, causing the dough to start spreading out. As it melts, it releases trapped water, and as the cookie gets hotter, the water expands into steam. It pushes against the dough from the inside, trying to escape through the cookie walls like Ridley Scott’s chestbursting alien.
When the temperature reaches 136°, it’s too hot for any salmonella that may have been squirming around in the eggs. They die off. You’ll live to test your fate with the raw dough from your next batch.