Holly, you can get clear vanilla at a cake decorating shop or the Wilton catalog. This works to keep your whites pure in cake and in white icing. Have you experimented with an oil based cake for lightness like a chiffon cake? The trick with them is to keep beating the egg white so much that you go past the gloss stage in them.
An angle food cake uses 12 egg whites beaten stiff with a simple syrup beaten in for sweetening.
Usually a sponge cake in the States is a cake that doesn't have egg whites, the leavening is beaten egg yolk and won't have anything like baking soda or baking powder in it.
I can't remember seeing anything in the UK that I would have thought of as cake. . . but then, why bother with a common cake when you can have all the shortbread you want? heeheehee
