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.
Ideal wine to accompany your Tagliatelle of leeks, soft-boiled egg: