A food, wonders Footprints? Indeed, my friend, I am happy to confirm that jelly roll is a food. A bit of an old-fashioned food, but a tasty treat nonetheless. Was the great Charles Mingus inspired to name his tune after the cake (for that's what it is, dear readers, as I'll explain more fully below) or after the late Jelly Roll Morton? I'll leave this debate to jazz aficionados more knowledgeable than myself, for Mingus, as we all know, was not given to lyrics, but was quite fond of wacky song titles (The Shoes of the Fisherman's Wife Are Some Jive Ass Slippers being my personal favourite). On, then, to food!
A jelly roll is, at its simplest, a sponge or angel (angel food) cake which is baked in a rectangular cookie sheet, so it is thin and flat - hence sometimes called a sheet cake - and then spread with jam or jelly and rolled along its long side into a log. Because it is prepared with inexpensive ingredients readily found in the North American kitchen, it was a favourite of Depression-era moms in particular. To serve, slice off pieces of the jelly roll, revealing a pretty nice spiral pattern of filling interlaced with cake. A jelly roll can be tarted up with a cream filling and an icing (frosting) coating, but the basic principle remains the same.
The trick to a successful jelly roll is to roll it up really tightly. The Joy of Cooking recommends letting the cake cool, then spreading the filling and rolling it up; Cook's Illustrated, never content with the easy way, suggests rolling the still-warm cake up in a tea towel, letting it cool, unrolling it, fillling, and re-rolling. Whatever. It'll be delicious either way.