Method:

1. Peel the potatoes, cut them once lengthwise and bring them to boil in cold salted water. 

2. Put on a casserole and caramelize the leeks (diced). Season with pepper, salt and nutmeg. Add the chicken stock and allow to braise until done. 

3. Portion the fish and arrange in a greased oven trey. Season with pepper and salt, some thyme, and allow to bake in the oven for about 7 minutes (180°C).

4. Drain the leeks and push out all excess moist. In case you opt to serve this dish with béchamel, mix the leeks under the béchamel. Make the béchamel slightly thicker than usual.

5. Drain the potatoes, put them back on the range, low heat, and allow excess water to evaporate from the potatoes.

6. Mash the potatoes and season with nutmeg, pepper, salt and add the eggs, milk and some butter. This mash should be juicy.

7. Take the fish out of the oven and drain excessive moist. Put a layer of leeks, then a layer of potato mash.

8. Add the breadcrumbs and allow to color in the oven.