Preheat the oven to 180 C / Gas 4. Using a wooden spoon or electric whisk, beat the butter and sugar together till light and creamy. Add in the vanilla at this point as the fat in the butter carries the flavour through.
Then add in the eggs one at a time, incorporating them well each time. If it seems to be curdling add a heaped tablespoon of the flour.
Once the eggs have been mixed in, sift the flour into the bowl from a height to add as much air as possible. Using a metal spoon fold the flour into the mix, leaving as much air in as possible.
Pour the mix into two suitable cake tins and bake for 30 minutes or until golden brown on top and it springs back when lightly pressed.
After the cakes have fully cooled, turn them out into a baking rack and spread jam over the top layer of one cake. Sandwich the two cakes together and dust the top with icing sugar. Enjoy.