together in a bowl. Set aside to soak while you make the pastry.
For the sweet shortcrust pastry
mix the flour and icing sugar together in a bowl. Add the cubed butter and rub it in lightly with your fingertips until the mixture resembles fine breadcrumbs. Alternatively
do this in a food processor or a mixer and then transfer to a bowl.
Mix the egg with the lemon juice and two tablespoons of cold water. Make a well in the centre of the flour mixture and pour in the egg mixture. Using a table knife
work the liquid into the flour to bring the pastry together. If it seems too dry
add a splash more water. When the dough begins to stick together
use your hands to gently knead it into a ball. Wrap in cling film and rest in the fridge for at least 15 minutes.
Preheat the oven to 180C/350F/Gas 4.
Once the dough has rested
cut it into two pieces
roughly one-third and two-thirds. Roll out the larger piece on a lightly floured work surface. Line a 20cm/8in pie dish with the pastry
leaving any excess pastry hanging over the edge. Spread the filling in the pastry case and dot with the butter.
Roll out the remaining pastry and cut it into eight long strips
roughly 1cm/½in wide. On a sheet of baking parchment
use the pastry strips to create a lattice with four strips going each way
passing them under and over each other.
Dampen the edge of the pastry in the tin with water
then invert the lattice from the paper onto the tart. Press the ends of the strips to the pastry base to secure.
Bake for 15 minutes
then turn the oven down to 160C/325F/Gas 3 and cook for a further 20 minutes.
Meanwhile
for the rum butter
beat together the butter and sugar
then gradually beat in the rum. Refrigerate until needed.
