Roast nuts a little in a pan, then crush them roughly. Remove the green of the leeks and wash the whites. Bring a pan of water to a boil and cook the leek whites for 15 minutes. Refresh immediately under cold water and drain.
Cut them into thin strips in length. Peel the shallot and chop it. In a bowl, mix with lemon juice, mustard, 2 oils, salt and pepper. Emulsify with a fork.
Bring water to a boil in a saucepan, gently immerse the eggs. Boil them for 6 minutes and then immediately pass them under cold water and reserve them.
In a salad bowl, mix the leek tagliatelle with the vinaigrette. Using a fork, roll up and place a generous nest of leek tagliatelle in each plate.
Place the eggs on top of the leeks, sprinkle with hazelnuts and serve quickly.