Place a medium pot on high heat add the salted water and bring to a boil. Add the broad beans, bring to a boil and simmer for a 1 ½ minutes.
With a slotted spoon take the beans out of the water in a bowl filled with water and ice to stop cooking and reserve their nice green color. Drain and peel the outside skin of the beans. Keep aside.
In the same pot over medium heat, pour 4 tablespoons of the oil and let it heat up for 1-2 minutes. Add the onions, and sauté for couple of minutes to soften but not to get brown.
Pour the vegetable stock and season with the salt and pepper. Bring to a boil and cook for 5 minutes. Add the artichokes and the lemon zest and cook for five minutes. Add the broad beans and the string beans and cook for 2 minutes.
Remove from fire and add the coriander and the mint. Stir and let the flavours come together for 15 minutes. Serve while drizzling the remaining 3 tablespoons of oil and the vinegar. Finally, top with the crumbled feta.