You might be tempted to bake 2 sheets of brownies at a time in the upper and lower thirds of the oven. Don't give in to this urge—they must go in the middle of the oven to cook through and brown evenly.
Cooks' note:
&183; Brownies keep, uncut in pan and chilled, covered (or cut and layered between sheets of wax or parchment paper in an airtight container), 2 weeks.