Peel and dice the potatoes, and boil them in plenty of salted water for 20 minutes. Drain, add a bit of extra virgin olive oil and mash with a fork.
Arrange the beans by cutting the ends of the pods, boil in salted water for 8 to 10 minutes, remove from heat and drain.
Clean the mushrooms and make thin slices raw with a knife.
Peel and finely chop the onion and crush the hazelnuts. In a bowl, add the onion, hazelnuts and vinegar. Beat with a whisk and add the extra virgin olive oil little by little without ceasing to beat.
Serve a potato base, arrange the beans, dress with the vinaigrette and decorate the mushroom slices.
4 servings