Or jam roll, really, since that’s what most people roll up in their génoise sheets. The big problem they have, of course, is cracking. But let’s face it, cake isn’t really designed to withstand the stresses that come into play when you wrap it up into a curlicue. Structures made of cooked starch and/or egg aren’t by nature elastic. In fact they’re usually downright brittle. Thus we bakers must employ everything in our proverbial trick bag to outwit it.
The most important of these tricks is baking the cake sheet just until the point of doneness, and no longer. The reason, because a well-browned, deeply caramelized crust is both overly thick and overly rigid. Try to roll it up and, well, you know what happens. Thus even the most meticulously formulated génoise recipe can be ruined by a careless execution.
Next, rolling the cake while it’s still hot. As all you bread bakers know, cutting into a loaf that’s fresh from the oven compacts the crumb into a paste. This is because the starch on the inside still has a wet, gelatin-like consistency. It needs an hour or so to set up. Jelly roll bakers take advantage of the starch’s temporary plasticity to mold it, turning it out onto a powdered sugar-dusted kitchen towel and rolling it up while it’s still steaming. After 10 minutes or so the cake is unrolled, at which point it can be filled and re-rolled without much difficulty.
There are a few other details that help too, like trimming off the hard edges of the cake sheet before the initial rolling. Some bakers even go to the extreme of trimming off the entire top crust. That to me is excessive, unnecessary (if you’re careful about your baking times) and a dreadful waste of cake. But Joe, what about the mixing stage? Isn’t there quite a bit that I need to be careful about there? Ah yes, indeed there is. More on that a bit later.