Butter is the star. Puff pastry has hundreds of thin butter layers sandwiched between dough. When that butter is ice-cold, it stays solid.
In a hot oven, the cold butter suddenly turns to steam. That steam explodes upward, pushing the dough layers apart. Boom—you get that airy, flaky magic.
If the butter gets warm before baking? It melts into a greasy puddle. Your pastry turns into a sad, flat cracker. Don’t let that happen.
