1-1/4 to 1-1/2 lb. medium Yukon Gold potatoes, boiled until tender, with skin
5 T extra-virgin olive oil
1 large yellow onion, diced
2 medium cloves garlic, minced
1/2 lb. watercress, stemmed
1/2 cup mascarpone
Sea salt and freshly ground black pepper
Scrub the potatoes as needed to remove any dirt, cover generously in water and simmer until cooked, but not overly tender. Drain and rinse under cold water then let cool. While the potatoes are cooling, heat 2 Tbs. of the olive oil in a 12-inch skillet over medium heat. Add the onion and a pinch of salt and cook, stirring often, until softened, about 5 minutes. Add the garlic and cook for 1 minute, then add the watercress. Season to taste with salt and pepper and cook, stirring, just until the watercress wilts, 1 to 2 minutes.?? Put the potatoes in a large bowl and break them into small chunks with a potato masher or large spoon, taking care not to over-mash. Add the watercress mixture, the mascarpone and the egg, mix to combine, and season to taste with salt and pepper. The potato mixture should hold together but not be too wet, and if necessary, add a little bit of breadcrumbs (or Panko) to attain the right consistency. Divide and shape the potato mixture into 16 equal patties, about 2 inches in diameter and ½ inch thick. (The cakes can be made to this point up to 4 hours ahead and refrigerated.)?? Heat the oven to 200̊F. Lightly oil a rimmed baking sheet. Heat the remaining 3 Tbs. olive oil in a 12-inch nonstick skillet over medium heat. Working in 2 batches, cook the potato cakes until golden on both sides, 3 to 4 minutes per side. Transfer each batch to the baking sheet, season lightly with salt, and keep warm in the oven for up to 30 minutes before serving. Serves 6-8.