Method:

1. Peel the potatoes and dice them in 2 cm cubes.

2. Boil them in salted water. 

3. Clean the leeks, cut them in half lengthwise and then cut them up in 2 cm pieces.

4. Bake the leeks on medium heat in butter and oil. Season with pepper, salt and nutmeg. Allow to sweat only, don’t caramelize. 

5. Deglaze the leeks with the chicken stock, add thyme and bay leaves and allow to simmer until done.

6. From butter, flour and milk make a béchamel. Allow the roux to dry out prior to adding the milk. The roux should smell like cookies before adding the milk.

7. Drain the leeks and add some of the stock to the béchamel.

8. Season the béchamel with pepper, salt, nutmeg and then sift it through a mesh strainer. Add the egg yolks and mustard and check for seasoning.

9. Now, to your béchamel, add your potatoes and leeks and keep warm on low heat.

10. serve