Has this ever happened to you? You bake a sheet of cookies until they are perfectly golden brown on their tops, but when you turn one over you get...
...cookies with burnt bottoms?
What causes this is the cookie sheet absorbing heat from the oven and conducting it into the cookie's bottom much faster that the tops. While there are two-layer cookie sheets that have an insulating air gap, the top sheet is still thick enough to cause this problem. Worse still, these insulated cookie sheets can't be adjusted to allow more of less heat through as needed to accommodate different baked goods.
A simple solution is to cover the cookie sheets with layers of paper towel topped with a sheet of aluminum foil.
The paper insulates the bottoms of the cookies and the foil prevents sticking. Because the foil is so thin it can't conduct enough heat sideways into the cookies to cause problems.
Varying the number of sheets of paper enables you to control how much insulation is in effect and in so doing control the amount of heat getting into the bottoms of the cookies. For example, medium thickness cookies, like the oatmeal cookies below, do best with two layers of paper.
Baked at the same temperature and for the same time as the first batch of cookies, these not only aren't burnt, but the bottoms are the same level of doneness as the tops. This means that simply by looking at the cookies you know how done they are on the bottom before taking them out of the oven.
Thinner cookies like sugar cookies do best with one layer of paper. Thicker, wetter cookies, like chocolate chip cookies, benefit from three layers. The increased insulation slows the bottom baking enough so the tops have time to develop a delicate crunch before the bottoms get too brown.
Every cookie sheet is different so some experimentation is needed to optimize results. For example, cookie sheet with dark surfaces absorb heat faster and may require and extra layer of paper toweling. Shiny cookie sheets reflect a lot of heat and may do better with one less.
The great thing about this technique is that it is applicable to a wide range of cooking projects. On my baking sheets, two layers of paper and one of foil allows the tops of my biscuits to brown at the same speed as the bottoms. This lets me know when they are done to perfection. I also use it on meatloaf, where it prevents the bottom over cooking to a burnt crust.
I hope you'll try this simple technique and that it helps you achieve more uniform baking. For those preferring videos, I've prepared the following:
Return to my main page to browse 60 other subjects