Place the flour in a bowl, then cut the butter into small
pieces and add in.
Rub both between your fingers until it resembles breadcrumbs,
add the egg and use a round bladed knife to mix together the
ingredients together with a cutting motion (a little extra cold
water may be needed).
When it forms a dough ball, cover and chill in the fridge for
Roll out the chilled pastry and line a buttered 20cm x 31cm
push up bottom tart tray.
Heat the oven to 200°C.
Using a mandoline, slice the onions finely.
Grate the cheese and place in a bowl, then add the seasoning
and toss to mix.
Transfer this to the pastry case, and spread out evenly.
Whisk the eggs and milk until blended and carefully pour over
the onion mix.
Place in the oven and bake for 25 minutes then reduce the oven
to 170c and cook for a further 20 minutes.
Leave to cool for 5 minutes then release from the pastry case:
Eat hot or cold.