Blanch shallots for 2 minutes in boiling water, then rinse with cold water and drain. Halve the shallots and fry for 2-3 minutes with 1 tablespoon of olive oil in a nonstick skillet. Ssprinkle with sugar. Add 100 ml (approximately 3 1/2 ounces) of broth, the vinegar and mustard seeds and cook until about half of the liquid has evaporated. Season with salt and pepper.
Rinse the potatoes and cook, with skin, in salted water for about 20 minutes. Rinse and cut the green beans into pieces, then boil in salted water for about 12 minutes. Rinse the green beans with cold water and drain.
Drain, peel and chop the potatoes. Mix with the green beans. Bring the remaining broth to a boil, pour over the potatoes and let soak for 20 minutes.
Pluck the radicchio into bite-sized pieces, rinse and spin dry. Rinse and halve the tomatoes. Rinse, shake dry and coarsely chop the parsley. Put all prepared ingredients in a large bowl. Drizzle with remaining olive oil and season with a little salt and pepper. Toss everything and serve.