Sift the flour and a pinch of salt into
a large bowl. Add the butter and rub in
until it resembles breadcrumbs. Stir in
the icing sugar, egg yolk and 3 tbsp cold
water, then quickly bring together to form
a firm dough. Wrap well in cling film and
allow to rest for 20 mins in the fridge.
Heat oven to 200C/180C fan/gas 6.
Roll out the pastry on a lightly floured
surface and line a deep 23cm tart tin.
Cover with baking parchment and fill
with baking beans. Cook for 20 mins,
then remove the paper and beans and
cook for 5-10 mins more until the tart
case is pale and sandy in texture (see p14
for tips on making and baking pastry).
Remove and turn the oven down to
160C/140C fan/gas 2. Spread the base
of the tart with the potatoes, onions
and cheddar. Whisk together the
eggs, milk and cream, then season.
Pour into the tart case and cook for
40-45 mins or until just set. Remove,
cool on a wire rack then serve.