Beat together butter, sugar, egg yolk and vanilla until light and creamy.
Sift flour and baking powder together and stir through creamed mixture.
Add enough of the lemon juice to make a firm dough.
Divide dough into halves, wrap in plastic food wrap and place in fridge for 15 minutes.
Filling
Soak bread in milk for 5 minutes. Squeeze excess moisture from the bread and place into a mixing bowl.
Soak sultanas and currants in water for 5 minutes and then drain.
Add remaining filling ingredients and blend together or squeeze mixture together with your hands.
Assembling the slice
Roll out one half of the pastry in between sheets of baking paper to roughly the shape of the slice tin. Trim pastry until it fits snugly in the bottom of the slice tin, leaving the bottom layer of baking paper.
Spoon filling into slice tin on top of pastry layer and use a spatula to ensure it forms an even layer.
Roll out the second half of the pastry in between sheets of baking paper to roughly the shape of the slice tin. Trim pastry until it fits snugly over the top of the filling in the slice tin, removing both layers of baking paper.
Whisk egg white together with a little water. Brush lightly over pastry. Sprinkle with additional sugar and prick with a fork.
Baking
Bake for 45 minutes or until golden brown.
Allow to cool for 20 minutes in tin before removing and allowing to cool on a cooling rack.
When cool, cut into squares.
Notes
SubstitutionsThis slice can also made with leftover fruit buns, fruit cake, hot cross buns and the like rather than bread. If substituting, just dial down the amount of additional fruit and spices you add to the filling depending on how fruity/spicy the items are you are using.TipsDon’t skip the refrigeration step when making the pastry. It makes handling the pastry a lot easier.BreadI used white bread with crusts on, but feel free to experiment.ServingServe hot or cold. It's lovely served warm with custard.StorageYour Chester Cake should last a few days, and you can store in or out of the fridge.