• 1-3/4 cups vegetable oil for frying
• 1-3/4 lb. (about 5 medium) low- to medium-starch potatoes, such as Yukon Gold, peeled
• 2-1/4 tsp. coarse salt
• 12 to 14 oz. onions (2 to 3 medium), diced
• 5 medium cloves garlic, very coarsely chopped (optional)
• 6 large eggs
• 1/8 tsp. freshly ground black pepper (optional)
1. In a large colander, place potatoes, sprinkle with 2 teaspoons salt. Let stand for 30 minutes. Pat dry with paper towels.
2. Heat oil in a large nonstick skillet over medium-high heat. Add potatoes and cook, turning occasionally, until crisp-tender, 10-15 minutes.
3. Add onion to potatoes in skillet; cook until onion and potatoes are soft, 5-8 minutes. Using a slotted spoon, transfer mixture to a large bowl; let cool slightly.
4. Add eggs to potato mixture; season with salt. Wipe out skillet. Heat 1/4 cup reserved oil over medium-high heat (chill remaining oil for another use). Add egg mixture, arranging potatoes to submerge.
5. Reduce heat to medium; cook tortilla until almost set, 25-30 minutes. Invert onto a large plate. Slide into skillet browned side up. Cook until golden on bottom and cooked through, about 4 minutes more. Serve warm or at room temperature. Cut into wedges.