Last week, I drew up some guidelines to follow if you wanted to try baking cookies in your car. This past weekend, since the temperatures were well over 100F out here, I decided to give the technique a try myself. I parked my car in full sunlight in the middle of the day, sliced up some cookie dough and started to bake.
I previously noted that most of the reporters and writers who tried this technique used refrigerated, slice-and-bake cookie dough. My guess would be that they chose to use that type of pre-fab dough because they might not be regular bakers and were looking for something that would be quick and easy, since the baking process using a car is not exactly fast. I went with a homemade dough, but decided that I, too, would use a slice-and-bake type of cookie (the recipe is at the bottom of this article). This meant that my dough could be prepared well in advance and that I could control the thickness of each cookie with precise slicing. Drop cookies work, too, but this seems to be the best way to control spread and ensure even cooking.
I sliced my dough into 1/4-inch thick slices and placed them on a parchment lined baking sheet. I used potholders to support the baking sheet (and to prevent any damage to my dashboard from the hot metal) and placed both the cookies and an oven thermometer in my car. 30 minutes later, the cookies were beginning to spread slightly.