To make the pastry, first sift the salt and flour into a big mixing bowl and rub in the butter until the mixture resembles breadcrumbs.
Mix in the egg yolk and sufficient water to bind the ingredients.
Knead the dough lightly and then chill for 30 minutes. Do not over work the dough as the result will be a hard base when baked.
Roll out the pastry on a lightly floured surface and then transfer to a pastry pan or dish. Roughly about ½ cm thick. Set aside. Preheat oven to 180°c.
Melt half the butter in a shallow pan, add oil and cook the onions until caramelised. Add the bacon and sauté lightly. Set aside.
Whisk eggs add heavy cream in a bowl before adding the nutmeg and season lightly with salt and pepper.
Spoon the cooked onions and bacon over the base of the pastry shell. Spreading evenly.
Pour in the cream and egg mixture slowly. Dot with the remaining butter.
Bake in a preheated oven at 180°c for 30 minutes or until set and golden brown.
Serve warm with a light vinaigrette side salad.