Blanch the beans for 2 to 3 minutes then plunge them into a bowl of ice water. Remove the skins. To book.
Heat a little olive oil in a saucepan, add the onion, garlic, cook for 1 minute, add the potatoes, half the broad beans, drizzle with vegetable broth, salt, pepper, cook 10 to 15 minutes until everything is cooked, then blend.
Put the yogurt in a bowl, add a little soup slowly while mixing. Then add to the soup.
Return to the heat, over low heat. Add the rest of the beans.
Toast the hazelnuts in a dry pan.
Serve the soup with the hazelnuts, garnish with fresh herbs, lemon zest and finish with a drizzle of olive oil and lemon.