What is dough chilling?

Resting shaped or mixed dough in the refrigerator before it bakes. Chilling firms the fat so cookies spread less and hold their shape and edges in the oven; it also hydrates the flour and gives enzymes time to break down starches, which deepens flavor — the toffee notes you taste in overnight-rested cookie dough. For cut-out cookies the cold is what makes a soft dough rollable and keeps the cut shapes crisp instead of slumping. Common range runs from 30 minutes (just to firm the butter) up to 48 hours (for full flavor development), depending on the goal.