1. To make a delicious Anglesey egg gratin with mashed potatoes, the first thing to do is to peel and wash the potatoes, and cut them into medium-sized cubes.
2. We cook in a saucepan with water, over medium heat, for 20 minutes, until tender. Then drain them and add the cream and half the butter.
3. We mash the potatoes until we obtain a puree. Separately we clean and wash the leeks and dry them. Then we cut the white part into thin slices.
4. Put the leeks in a saucepan and add water, and cook for 10 minutes, until tender. Reserve in a bowl.
5. Cook the eggs in another tray with salted water, over medium heat, for 10 days, then rinse them with cold water and let them cool.