Put the flour, butter and salt into the bowl
of a food processor, then pulse until the mix
looks like fine crumbs. Splash in 4 tbsp cold
water, then pulse to a dough. Turn onto a
lightly floured surface, shape into a smooth
disc, then wrap and chill for at least 10 mins.
Heat oven to 200C/fan 180C/gas 6.
Roll pastry out on a floured surface until
large enough to line a 23cm loose-bottomed
tart tin. Line the tin with the pastry, leaving
any excess pastry overhanging. Line with
baking paper, then fill with baking beans.
Bake on a baking sheet for 15 mins. Take out
the paper and beans, then bake for 10 mins
more until pale golden and cooked.
While the pastry cooks, soften the onions
in the oil over a medium heat for 10 mins
until golden. Beat the eggs and cream
together, then season to taste. Crumble
up the hard cheeses and chop or pull the
creamy cheese into small pieces. Scatter
the cheese into the pastry case, add the
onions, then pour in the egg mix. Turn
the oven down to 160C/fan 140C/gas 3 and
bake for 40 mins until set and lightly golden.