This dish is ridiculously simple but for years I could never make it as well as the marinated potatoes served at Bodeguita Romero. Then one day I happened to be sitting at the bar when Pedro Romero started mixing up the house potatoes for the day and I discovered that the secret ingredient was vinagre de jerez. I believe Pedro was using a Pedro Ximenez vinegar, but I’ve since made this with the Reserva (aged in oak) and the potatoes come out AMAZING. I usually use small new potatoes, but any semi-waxy potato will do. I also noticed that Pedro didn’t use any utensils to toss the potatoes. Instead he picked up the large pot he was using as a receptacle by the side handles and tossed the whole thing up in a smooth rotating motion several times until the ingredients were well mixed.
Instructions below the links.