Leek and onion tart with blue cheese

Yesterday, I posted a recipe to use unused egg whites. This post brought a very smart question: "What do you do with the yolks?"
The answer to this question is multiple and I will dedicate a post to recipes that will use only yolks or only egg whites, as long as I feed this blog.
In my case, the question could have been "What did you do with the yolks?"
This question was an easy one: I made a leek and onion tart.
A tart - not a quiche - this tart was inspired by the classic French onion tart with a twist: leeks and blue cheese.* By contrast with the quiche, this tart filling is creamy and delicate. It can be served as a light dinner or as an appetizer with a glass of Pinot Gris.

Ingredients (8 servings)

For the pastry:

- 160g flour
- 70g butter, diced, at room tempreature
- 50ml water
- a pinch of salt
For the busiest cook, just use an industrial savoury pastry - you'll save about 10 mins.

For the filling:

- 2 leeks

- 2 large onions, sliced (French cut)

- 3 tbsp flour

- 200ml chicken stock

- 250ml milk

- 5 yolk

- 30g mild cheese, finely shredded

- 30g blue cheese

- 1 tbsp olive oil

- salt, black pepeer

Instructions (1 hour)

Preheat the oven at 200C, fan bake.

1. Make the pastry: mix the flour, the salt and the butter until you get a fine crumble. Add the water gradually and mix until it forms a ball. Cover and rest in the fridge.

2. Cut the white part* of the leeks in fine strips. Slice the onions.

3. Melt the butter in a pot and add the leeks and the onions. Season with salt and pepper. Cook on medium heat, stir often, until they are soft like in a leek fondue (about 15 mins).

4. Take the pot out of the heat and sift in the flour. Stir briskly to avoid lump formation.

5. Add gradually the chicken stock while you put the pot back on the heat. Stir to avoid lumps formation.

6. Continue by pouring in the milk, gradually. Stir until it thicken a little (about 5 mins).

7. Reduce the heat to minimum and whisk in the yolk, one by one to avoid the yolk to scramble.

8. Check the seasoning. Turn the heat off.

9. Line the bottom of a tart tin. Roll the pastry and lay it over a tin. Prick all over the pastry with a fork.

10. Spread the leek and onion fondue over the pastry.

11. Sprinkle the cheese over the top.

12. Bake in the oven for 35-40 mins.* 

Serve with crudités.

Bon appétit!

Tips

* You could also add some bacon strips (about 100g) that you will cook in the butter, just before you add the leeks and the onions. It will bring a gentle smoked flavour to the tart.
* Keep the green part of the leeks to make a stock (chicken or veggie stock) or a soup.* Always keep an eye to find the right timing for your oven. If the top of the tart gets too brown, cover with foil and continue baking.