How do you brown cookies when stacking cookie sheets in oven?

It is generally not recommended to stack cookie sheets in the oven as this can cause uneven baking and browning of the cookies. When stacking cookie sheets, the heat cannot circulate properly, which can result in the cookies on the top sheet overbaking while the cookies on the bottom sheet remain underdone. Additionally, the cookies on the bottom sheet may not brown as well as those on the top sheet due to the lack of direct exposure to the heat source.

If you need to bake multiple batches of cookies at once, it is best to use multiple ovens or to bake the cookies in batches, rotating the cookie sheets between the top and bottom racks as needed to ensure even browning and baking. Using convection bake (if your oven has this setting) can also help to circulate heat, allowing the cookies to brown and bake evenly.