Step by step recipe:

1. 10 min.
   Line the mould or tin with pastry, prick base all over, then keep in the fridge.
2. 40 min.
   Peel 4 potatoes, wash and cook them in salted water, until they are just tender.
3. 5 min.
   Allow to cool then cut into fairly thick slices.
4. 20 min.
   Wash and slice thinly 1 leek and 1 shallot.
5. 5 min.
   Heat 3 tablespoons olive oil in a pan over medium heat, add sliced shallot, salt and pepper and cook for a minute or two.
   
   Add leek, salt and pepper, and cook a few minutes without letting it colour.
   
   Set aside.
6. 5 min.
   If you wish to add 125 g small pieces of bacon, cook in a frying pan without fat and add, at the last minute, a tablespoon of vinegar.
7. 3 min.
   Cut 250 g Maroilles cheese into thick slices, including crust.
8. 5 min.
   Prepare mixture by mixing with a whisk: 2 egg yolks, 1 egg, 250 ml liquid cream, salt and pepper.
   
   Set aside.
9. 3 min.
   Preheat your oven to 410°F (210°C).
   
   Put a layer of leek into the pastry case.
10. 3 min.
    A layer of bacon (optional).
11. 3 min.
    Cover with a layer of potato slices.
12. 2 min.
    Pour in the mixture.
13. 3 min.
    Arrange cheese on top.
14. 40 min.
    And put in bottom of oven for around 30-40 minutes.
15. 
    The tart is ready when it is nice and golden brown.
    
    Serve to your guests, warm if possible, with a green salad.