Hagbech Onion Tart

An essential aspect of this onion tart, with it's thin crisp pastry base and a rich creamy filling, is the cooking of the onions. Whereas in my cheese and caramelised  onion bread click here for the recipe the onions need to be taken right to the limit of browning, the onions for this recipe need long slow cooking, rendering them translucent and barely beige, sorry that does sound a bit like a new season's shade from some fashion house, when all it means is only the slightest of colour.

In order to achieve this, cook the onions on a low heat with a scant teaspoon of salt, half a teaspoon of white pepper, three bay leaves and quarter of a nutmeg grated in 10g of unsalted butter for a good 30 minutes.
The recipe for the pastry makes twice as much pastry as is required for this tart but it's so much easier to make in this quantity and since it freezes really well, it's what I chose.

For this recipe you will need,
For the pastry,
250g of plain flour
130g of unsalted butter
1 small egg
1 teaspoon of caster sugar
1/2 teaspoon of salt
40ml of water

For the filling,
600g of sliced onions (peeled weight)
4 eggs and an extra yolk
200g of double cream
200g of milk
10g of unsalted butter
1/2 nutmeg grated
2 teaspoons of salt
1/2 teaspoon of white pepper
3 bay leaves

Begin by cooking the onions as described above. Slice them about 1 centimeter thick and cook on a low heat in a heavy based pan with a lid. Keep an eye on them and stir every 5 minutes or so to avoid any of the onions catching on the bottom of the pan. Set aside to cool

Meanwhile make the pastry by placing the butter, salt, sugar and egg in a food processor and process until you have a sticky paste. Add the flour and pulse a few times until you have even sized crumbs, finally trickle in the water while pulsing the processor until you have a ball of finished pastry. Wrap in cling film and set aside to rest for an hour. Since this recipe requires only half of this pastry, you can freeze the other portion at this point or keep it in the fridge for up to a week.
Roll out the half portion of the pastry to fit a 25cm fluted, loose bottomed tart tin, place the lined tin in the fridge to chill for 30 minutes. Heat the oven up to 180C and after lining the pastry with parchment paper and baking beans, bake the tart shell for 20 minutes. Remove the parchment and beans carefully and return the tin to the oven for a further 10 minutes with the heat turned down to 160.
Make the filling by whisking together the eggs, cream, milk, the remaining teaspoon of salt and finally fold in the cooked onions.
When the tart shell is cooked, pour in the filling and return the tart to the oven to cook for 30 to 40 minutes at 160C. The tart should still have a slight wobble in the middle and take on a golden brown colour at the edges.

Notes:
I find placing most of the filling in the tart shell before returning the tart to the oven then pouring in the remainder using a jug once the tart is on the oven shelf helps avoid spillage.
I place the bay leaves on top of the tart, more as a decoration than anything else but somehow they still impart a little flavour.