Make a well in 120g of plain flour and a pinch of salt.
Put butter, castor sugar, a tiny drop of vanilla essence and two egg yolks in well. With one hand, fold the mixture together.
Start with the central ingredients and then slowly incorporate the flour from the outside. Don't use a food-processor in this case as it tends to overwork the pastry.
Bring the ingredients into the centre with a pallet knife. Roll until all the ingredients are incorporated.
Place the mixture onto grease proof paper, wrap it quite tightly and place in the fridge for one hour.
Remove from the fridge, unwrap and place in the centre of another piece of greaseproof paper.
Roll the dough slightly, tidy it up so that it forms a circular shape, scallop the edges and then prick the base with a fork a few times. This helps to make sure that the heat is distributed evenly across the pastry so that it all cooks at the same temperature and stops any puffing that may occur.
Slide the grease proof paper off the bench onto a pan for cooking.
Place in oven for about 15 minutes at 195°C on the middle to top shelf. You don't want the pastry to brown, so you need to watch it carefully.