Sieve the flour and salt into the food processor bowl. Cut the butter into pieces and add to the flour.
Whizz the mixture until it resembles fine breadcrumbs. While it is still whizzing add the egg yolks and just enough water to combine the dough. Wrap the dough in cling film and place in the fridge for 30 minutes.
Preheat the oven, Gas Mark 6, 200°C (400°F) Roll out the pastry thinly. Line a 28cm flan/quiche dish. Remove any air pockets. Prick the base with a fork and bake blind for 15-20 minutes.
To Make the Filling: Cook the streaky bacon in a hot pan until crisp. Add the leeks and continue to cook for 3-4 minutes. Remove from the heat.
In a large bowl beat the eggs, creamed cheese, mustard, cayenne pepper and seasoning together. Add the leeks and bacon. Pour the filling into the baked pastry case and bake for a further 35-40 minutes.
Serve warm. A mixed leaf green salad makes the perfect accompaniment.