A perfect vehicle for sweet, slow cooked onions
The key to this recipe is its simplicity, you can add some bacon or lardons but I prefer to let the sweet, slow cooked onions do all the talking.
For the pastry:
180g plain flour
Pinch of salt
90g unsalted butter, cubed and straight from the fridge
1 beaten egg
1-2 tbsp cold water
For the filling:
75g unsalted butter
3 brown onions, finely sliced
Pinch of salt
3 egg yolks (reserve the white for brushing the pastry case)
250ml double cream
A little grated gruyere cheese (optional)
A few thyme leaves (optional)
Grated nutmeg (optional)
Remember to make your pastry ahead of time and chill for at least half an hour. Sift the flour and salt into a bowl and then rub in the butter until you have a breadcrumby texture.
Add the beaten egg and just enough water to bring the dough together. Flatten the pastry into a thick disc, wrap and rest in the fridge.
Roll out the pastry to fit 4-6 individual tart tins (depending on size) or a 30cm tart tin.
Melt the butter in a pan, add the onions and salt, now cover and cook very gently for up to an hour until the onions are meltingly soft but not browned. Remove the lid and cook for a few more mins to evaporate any liquid. Leave to cool.
Mix together the egg yolks, cream, salt and pepper and add the onions. Pre-heat the oven to 200C and blind bake the pastry (weighted with baking beans or rice) for about 15 mins, prick the base with a fork and brush with a little beaten egg white. Turn the oven down to 180C and bake for a further 5 mins.
Now spoon the onion mixture into the pastry case(s) and bake for about 20-25 mins for individual tarts, 30-40 mins for a large tart, until set and lightly browned (a little grated cheese does help the top to colour).