Boil the baby potatoes in salted water for around 20 minutes until cooked; you should be able to easily pierce the potatoes with a skewer.
While the potatoes are boiling, in a large bowl combine the extra virgin olive oil, Jerez vinegar, salt, and white pepper, add the 2 pitted and crushed olives, capers, torn anchovies, and a third of the rucola leaves, and toss to combine.
Drain the potatoes, run a little cold water over them, peel off the skins, slice them in half, and toss them into the bowl, combining everything well. Taste, and add more salt or pepper if needed.
If serving a warm potato salad, transfer to a serving plate immediately, arrange the remaining rucola on top and, if you like, drizzle a little more extra virgin olive oil, grind on fresh black pepper and sprinkle on some chilli flakes (optional).
If opting for a cold potato salad, refrigerate and add the rucola and pepper/chilli flakes just before serving.