Instructions: Line bottom of two 7" sandwich tins with greaseproof paper and grease lightly. Sieve dry ingredients into a bowl. Separate yolks from whites of eggs. Mix corn oil, yolks and water together lightly with a fork.

Stir the mixture into the dry ingredients and beat well to form smooth, slack batter. Whisk egg whites until stiff and fold lightly into mixture. Turn into tins and bake in moderately hot oven (375F. Mark 5) for 25-30 minutes. Cool on wire tray. Sandwich together with jam and dust with caster sugar or top with icing.

Variations:
Chocolate flavour - replace cornflour with equal quantity of cocoa.

Coffee flavour - add two teaspoons instant coffee powder to liquid ingredients and mix well before combining with dry ingredients.

Orange or lemon flavour - add the grated rind of half an orange or half a lemon to the ingredients.

Notes:
All these notes are my own, and bear in mind that theyre mostly aimed at people who are less-than-confident about cake-making, and/or people who have limited cooking facilities, kitchen equipment, or money.

This recipe is really practically unbreakable (and TBH I think most cake recipes, possibly most recipes in general, are a lot more robust than a lot of people think). Some examples of its non-breakableness:

You dont have to use Mazola Corn Oil; that bit is purely a marketing gimmick. Ive used bog-standard cheap vegetable oil, supermarket own-brand corn oil, real Mazola, and Mazola lite, and never noticed any difference.

I often dont bother to sieve the dry ingredients, and at the moment I dont even
*own* a sieve (although I did have to shove the cocoa for the chocolate version through a tea-strainer because it was so lumpy!).

The folding lightly (which scares a lot of people off lots of recipes) is less fragile than people seem to think, and will cope with a fair amount of inexpert folding (like what I do!) - basically just so long as you dont
*beat* it or mix too hard, itll be fine. The point of it is to keep the air in the whisked egg whites - this is what makes the sponge light and fluffy. The worst that will happen if you do it badly is that your sponge will be a bit heavy.

The 25-30 minutes is by no means exact and will largely depend on your oven. (By the way, that 375F is equal to 190C.) Fan-assisted ovens generally need 10 degrees knocking off the temperature (this is a general rule, not just applicable here; apologies to anybody for whom this is a really obvious thing to point out). Basically, though, cook it until its done (see below).

How to tell if cakes like this are cooked: stick a sharp knife or a skewer or something in it, right in the middle because thats where its likely to be thickest (and therefore take longest to cook). If the knife comes out clean the cakes probably done; if the knife comes out sticky it probably needs a bit longer.

Apparently if you open the oven too often while its cooking, a cake can collapse. Ive never had this happen to me and Im often terribly impatient and keep opening the oven to look. Probably not worth worrying about unduly, to be honest.:-) (I only mention it because it was something I used to be really worried about!)

Obviously (well, sorry if it isnt obvious!) you dont have to make a sandwich sponge cake - it does just as well for a solid sponge.

Actually, this isnt obvious, I remember it occurring to me that it might not cook properly if all that cake mix was in one tin. So let me assure you that it does work (but takes a bit longer to cook), and even works fine with double quantities, although cooking time will need adjusting (takes about an hour in my oven). Double quantities does a 10" cake about right. Ive never tried more than double, probably not advisable since even double-quantities is getting dangerously near to burning on top by the time it cooks in the middle.

Separating eggs is slightly tricky, but comes with practice (and is made completely trivial if you have an egg-separator, but Ill assume people havent since most people dont seem to). Crack the egg carefully, just enough to get your nail into the shell and split it in half. The aim is to keep the yolk in the shell and pour the white out

(I find transferring the yolk from shell to shell to get the bits underneath it out helps). A bit of egg-white getting in the yolks wont do any harm; but a bit of yolk in the whites will make it very difficult to whip the whites until theyre stiff. It takes ages if youre just using a fork or an egg-beater, although its possible - a rotary-whisk is useful here (but not a blender, they over-beat the eggs and dont get enough air in - or so I find at any rate), but it still takes a while and you really want the whites to be stiff enough to stay in peaks when you lift a bit up. This is what makes the sponge light. I suspect a sponge cake with only partially-stiffened egg whites would be edible but a bit flatter and heavier.

Baking parchment (or greaseproof paper, which is cheaper and just as effective) really does help - I grease both the inside of the tin and the inside of the paper with margarine. The latter stops the cake sticking to the paper (its a bastard to peel off sometimes!) and the former makes the paper stick to the tin so you can pour the cake mix in without the paper falling in! However if you dont have baking parchment or greaseproof, its still do-able; just make sure the cake tin is really well greased, and when its cooked slip a knife round the side before trying to get the cake out.

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