Rory's potato, gruyere (coolea), bacon and thyme leaf pie

Method

1. Preheat oven to 180c
2. Peel the potatoes and slice thinly to the thickness of a coin. I use a Japanese mandolin for this task though you can use a knife or the appropriate slicing blade of a food processor. Place in a saucepan and cover with cold water. Add a pinch of salt and bring to the boil.
3. Remove from the heat immediately, strain and rinse with cold water to stop them from cooking any further at this stage. Lay the potato slices out on a clean and dry t-towel and pat them dry.
4. Divide the puff pastry into two pieces, - a larger piece, 500g to line the tin and a smaller piece 250g for the lid.
5. Roll out the larger piece and use it to line the tin pressing it well into the base and sides of the tin. I usually leave a ½ cm overhang of pastry over the edge of the top of the tin to assist with sealing the filled tart later. Chill until later. Roll out the smaller piece of pastry to comfortably fit the top of the tin and chill until needed.
6. Heat 2 tablespoons olive oil in a heavy bottomed saucepan and add in the sliced onions and thyme leaves.
7. Toss well, cover with a disc of greaseproof paper and the saucepan lid and cook over a very gentle heat so that the onions soften completely without colouring. Cool completely.
8. Place the lardons of bacon in a saucepan of cold water and bring to the boil. Strain and rinse briefly and dry on a clean t-towel.
9. Heat 1 tablespoon of oil in a sauté pan, add the lardons and stir and cook until a light golden colour is achieved. Remove from the pan and reserve any liquid bacon fat from the pan.
10. To assemble the tart filling, place the potatoes, onions, bacon, thyme leaves and cheese in a large bowl. Beat the egg yolks and cream and season with salt and pepper. Add this to the potatoes and mix well. Taste a little of the liquid to check that the seasoning is correct.
11. Place the filling in the lined tart shell. Brush the rim of the pastry with a little beaten egg and place the lid on top. Pinch the top and sides of the pastry together to make a neat and tight seal.
12. Brush the top of the pastry with a little more beaten egg and place in the preheated oven.
13. Cook at this temperature for c 1 hour. If the pastry appears to be colouring too much, lay a sheet of grease-proof or parchment paper over the top. After 1 hour use a skewer inserted through the pastry to ascertain that the potatoes are tender and cooked.
14. The cooked tart is best served hot but not bubbling straight from the oven. I usually allow it to rest for 10 minutes at room temperature before bringing it to the table. Otherwise you can keep the tart hot in the oven reduced to 100c for at least 30 minutes.
15. Serve the tart cut in slices on hot plates with a salad of leaves to accompany.