1. In a large pot, cover potatoes with cold water and cook over medium-high heat until easily pierced with a knife, about 15 minutes. Drain well.
2. Preheat oven to 400 degrees F. While potatoes are cooking, heat oil in a large nonstick ovenproof skillet over medium-high heat. When oil is hot, saute onion for 5 minutes, until softened and translucent.
3. In a large bowl, lightly beat eggs and egg whites with salt and pepper until well combined but not too foamy. Add potatoes, goat cheese, and marjoram and mix to combine.
4. Pour egg mixture into pan with the onions, pressing mixture into an even layer with a spatula and shaking gently to prevent sticking. Reduce heat to medium and cook until golden brown on bottom and almost set, about 10 minutes. Place skillet in oven and cook until tortilla is completely set, about 5 minutes.
5. Gently loosen from pan. Place a serving plate over the skillet and invert the tortilla onto the plate. Serve warm or at room temperature, sliced into wedges.
Source: Hannaford fresh Magazine, November - December 2009