Boil the potatoes with their skins on, then peel and cube them after cooling under cold water.
Cook the green beans briefly and add them to the potatoes. Throw in cherry tomatoes, sliced red onions, olives, and capers.
Season with salt, pepper, and Sicilian oregano. Finish with a drizzle of olive oil and white wine vinegar, mix well!
Tip: this can be made ahead of time and kept cool in the refrigerator until serving!