- 1/4 cup plus 1 tablespoon extra-virgin olive oil, plus more for brushing
- 2 medium Yukon Gold potatoes, peeled and thinly sliced
- 1 medium white onion, thinly sliced
- 4 thin slices of serrano ham (1 ounce), torn
- Salt and freshly ground pepper
- 8 large eggs, beaten
- 2 teaspoons red wine vinegar
- 1 bunch watercress, thick stems discarded
- Preheat the oven to 350°. In a medium, nonstick ovenproof skillet, heat 3 tablespoons of the olive oil. Add the potatoes and cook over moderate heat, turning and stirring occasionally, until the slices are tender and beginning to brown, about 7 minutes. Add the onion and cook, stirring occasionally, until softened, about 3 minutes. Stir in the slices of serrano ham and season with salt and pepper.
- Season the eggs with salt and pepper and gently stir them into the skillet. Cook over moderate heat until the eggs are just beginning to set at the edge, about 3 minutes. Transfer the skillet to the oven and bake the frittata for about 12 minutes, until the eggs are completely set.
- Meanwhile, in a large bowl, whisk the vinegar with the remaining 2 tablespoons of olive oil. Add the watercress, season with salt and pepper and toss.
- Cut the frittata into wedges and serve with the watercress salad on the side.
The Spanish would drink red wine with this variation on a classic tapas dish. Rioja is a great choice.