Preheat the oven to 180 °C. Line two 18cm cake tins.
Cream the butter and castor sugar together until softened. Add the vanilla essence and gradually beat in the eggs, one at a time. Do not worry if the mixture looks split as the flour will bring it together again.
Sift the flour, baking powder and salt together.
Fold the flour mixture spoon by spoon into the creamed mixture, adding alittle water each time to form a batter with a soft dropping consistency.
Divide the mixture between the prepared cake tins and bake for 15–20 minutes or until an inserted skewer comes out clean.
Remove from the oven, turn out of the tins and allow to cool on racks.
Sandwich together with jam of your choice and dust with icing sugar.