- 1½ pounds russet potatoes, peeled and cut into large chunks
- ½ red onion
- ½ cup cider vinegar
- ½ teaspoon dried oregano
- Salt and freshly ground pepper
- 2 ounces fresh mozzarella cheese, cut into 4 equal pieces
- 2 tablespoons plus ½ cup olive oil
- 1 large cucumber, peeled, halved, seeded, and cut on the diagonal into ¼-inch-thick crescents
- 2 avocados; pitted, peeled, and cut into ½-inch dice
- 1 large, ripe tomato, cut into bite-sized chunks
- ½ small head iceberg lettuce, shredded
- Preheat the oven to 325°F. Put the potatoes in a large saucepan with cold salted water to cover and bring to a boil over high heat. Cook until tender, about 10 minutes. Drain well, scatter on a baking sheet, and let cool for several minutes. Place in the oven to dry out, about 5 minutes. Let cool, then press through a ricer, the large holes of a box grater, or a colander.
- While the potatoes are in the oven, cut the onion half into quarters and slice thinly to yield slim pieces about 1 inch long. Put in a nonreactive bowl with the vinegar and oregano and let rest for 15 minutes.
- Season the potatoes with salt and pepper, then divide into 8 equal balls. Place a ball in the palm of your hand, top with a piece of cheese, and then a second potato ball. Shape the potato around the cheese to form a 4-inch patty. Repeat with the remaining potato balls and cheese. (The recipe may be prepared to this point, covered, and refrigerated up to 1 day before cooking.)
- Heat the 2 tablespoons olive oil in a nonstick skillet over medium heat or in an electric frying skillet set at 350°F. Add the polpette and cook, turning once, until brown and crispy on both sides, about 10 minutes total.
- While the polpette are cooking, finish making the salad. Whisk the remaining ½ cup olive oil and salt and pepper to taste into the onion-vinegar mixture. Add the cucumber, avocados, and tomato and toss well.
- Arrange a nest of lettuce on each of 4-plates. Spoon the salad over each nest. Top with a polpette and spoon more dressing over all. Serve at once.