This is my tried-and-tested-and-approved-of-by-paying-customers recipe:
If you follow it Very Carefully it is fool proof!
For a 9" cake you'll need 7 medium eggs.
Grease and line the bottom of the tins with a circle of greaseproof/baking paper. Heat the oven (non fan, if you've got one) to 160 degrees.
Weigh the eggs with their shells on. Then use the same weight of Stork (in the tub NOT the foil wrapper)/self raising flour and caster sugar. So if the eggs are 245g you'd use 245g of all the other ingredients.
Beat the stork until it's soft then add the caster sugar and beat it for 5 minutes so it's very light and fluffy. You really need a hand mixer or food processor with beater for this unless you've got very good arm muscles. Don't skimp on the beating, it's how you get lots of air in the mix so it rises.
While it's beating lightly beat the eggs together with a fork and add a tsp of vanilla essence and a tbsp of milk.
Once the marg/sugar mix is beaten add the egg mixture a bit at a time with a spoonful of sieved flour. Beat well after each addition.
Once you've added all the egg mixture sieve in the rest of the flour plus a couple of extra heaped tablespoonfuls and thoroughly mix in using a metal spoon. You want to be fairly gentle with this bit so you don;t batter all the air out of the mixture.
Split it between the tins and bake at 160 degrees for around 40 mins - they should have risen, be smooth on the top and a light golden colour (don't open the oven door before then or the cakes will sink).
If you stick a skewer in the middle it should come out clean and if you listen to it there should be a few bubbling noises - if it's bubbling furiously, give it another 5-10 mins.
Good luck!