If I ever open the oven door while something is baking, heat will inevitably escape, lowering the temperature, extending the baking time, and potentially causing the pastry or cake to lose moisture.
Opening the door too early can be especially damaging to delicate bakes like cakes, soufflés, and choux pastry, since the sudden temperature change can interrupt the rising process and cause them to sink or collapse.
As tempting as it is to peek, I always keep the oven door closed for at least the first two-thirds of the recommended baking time.
Whenever I need to check the progress, I’ll use the oven light and watch through the window, then open the door only when I’m ready to rotate the pan or test for doneness.
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