Jelly Slices
Bake a sheet of Genoise cake, or any mixture you are used to that will bake level and not rise, rounded over in the middle, and have it less than an inch thick when done. Turn it out of the pan, bottom side up, cut in long strips, split them and spread with red fruit jelly or jam same as jelly cake. Stir up a pearl glaze and spread over the top of the strips of cake. This glaze or icing can be made with water as well as with white of eggs, just enough to wet the powdered sugar so that it can be spread smoothly, and can be made pink by using fruit juice instead of water. When these large strips or jelly cake have been iced over with it, cut them with a knife dipped in hot water, into long and narrow pieces and set them a little distance apart on pans for the icing to dry.
A sheet-cake assembly rather than a baked recipe: the only real technique is getting the icing to the right consistency and cutting cleanly through it. Everything hinges on a flat, thin cake.
- The cake must bake levelA genoise baked in a shallow sheet pan will dome very little, and spread thin it will stay well under the inch the recipe allows. Turning it out bottom side up, as directed, hides any unevenness and gives a smooth surface for the glaze.
- OvenFor a thin sheet genoise, 350-375F for 10-14 minutes. The book assumes you already know your own cake; bake until it springs back and the edges just begin to pull away, and no longer, or the strips will crack when split.
- "Pearl glaze"Here it appears to mean a thin flat icing: powdered sugar moistened with just enough liquid to spread, which dries to an opaque matte shell. Water gives the plainest version, egg white a harder and glossier one. Start with about 2 tablespoons of liquid per cup of sugar and add more a few drops at a time.
- If you use egg whiteAn icing made with raw white and left to air-dry is not cooked at any point. Pasteurized egg whites or meringue powder give the same set without the uncooked-egg question; plain water or fruit juice avoids it entirely.
- Colouring with fruit juiceStrained raspberry, currant or cranberry juice both tints and thins the icing, so hold back the water and add it by the teaspoon.
- Split and fill before icing"Same as jelly cake" means a thin layer of jelly between two thin layers of cake. Warm the jelly slightly and beat it smooth so it spreads without tearing the crumb; a stiff jam will lift the surface.
- The hot knifeThis is the step that decides how the slices look. Dip a thin-bladed knife in hot water and wipe it between every cut; a dry blade drags the setting icing and chips it. Cut while the glaze is still tacky, not fully dry.
- Drying and yieldDrying -- Set the cut pieces apart on a rack or pan for an hour or two until the icing is dry to the touch, then they can be stacked. Yield depends on how wide the long strips and the cross-cuts are made.
Jelly slices belong to the American bakery counter of the late nineteenth century, when a shop might make up one large sheet of cake, split, filled, iced flat and cut down into uniform pieces. The method explains the recipe's offhand tone: the author assumes a working pastry cook with a standing genoise or hot-milk sponge formula and a bowl of powdered sugar, and spends his words only on the glaze and the hot knife. The sugar-and-liquid coating had the commercial virtue of drying hard enough for the slices to be stacked and handled. The same construction survives in the British bakery slice.