For the pastry
For the filling
Preheat the oven to 180°C/350°F/Gas mark 4. Grease a medium-sized baking tin.
To make the pastry, sift the flour into a bowl and rub in the butter. Add a pinch of salt to 50ml/2fl oz water, then gradually add to the bowl until the mixture forms a ball. Roll out and use to line the bottom of the tin.
For the filling, sweat the onions in the boiling water for 5 minutes. Drain.
Fry the bacon in a little of the butter until crisp. Add the remaining butter, onions, mixed herbs, salt and pepper, and cook for 15 minutes.
Beat the egg yolks and cream together. Add to the onion mixture, and pour into the baking tin. Bake in the oven for 40–45 minutes. Serve hot.