Separately, boil the potatoes, unpeeled, and the green beans. The potatoes should be placed in cold water and brought to a boil, while the green beans should be put in boiling, salted water. Then the vegetables are al dente, drain and let cool. Peel the potatoes and place on a serving dish. Divide the green beans into 8 bunches and tie together with the chives. Arrange on the plate with the potatoes. Finely chop the white onion. Peel the tomato, remove the seeds and roughly chop. In a bowl, mix the onion, tomato, finely chopped parsley and salt 5 tbsp oil. Mix until uniform and drizzle on the vegetables just before serving.