Heat a cast iron skillet or comal over medium heat. Add chiles and toast on all sides until fragrant and darkened in color. Transfer to a bowl and cover with hot water. Let soak 30 minutes.

Add onion and garlic to the skillet and cook until browned and toasted on all sides. The garlic will toast sooner than the onion, so remove it before it burns. Transfer to a blender.

Add orange zest and juice, sherry vinegar, and salt to the blender with the onions and garlic. Remove the chiles from the soaking liquid (saving the liquid) and place in the blender. Add 6 tablespoons of the soaking liquid to the blender and blend until smooth. Add more liquid, a tablespoon at a time, if it seems too thick. Taste and add more salt as needed.

Transfer to a covered jar and set aside. You can make the salsa up to a week in advance and keep covered in the refrigerator until ready to use.

Cover potatoes with water in a medium saucepan. Add a generous pinch of salt and bring to a boil. Boil until soft, drain and return to the pan. Add garlic, white pepper, cumin, and salt to taste. Mash potatoes until mostly smooth, its okay if a few small pieces remain.

Heat a cast iron skillet or non-stick skillet over medium heat. Warm tortillas one at a time in the dry skillet, toasting lightly on both sides. Place about 3 tablespoons of the potato filling on one half of each tortilla and fold in half to close.

Add oil to the cast iron skillet and heat over medium heat until a piece of bread browns in 30 seconds. Add tacos a few at a time and fry until crisp and brown, about 2 minutes per side. Transfer to a paper towel lined baking sheet to drain.

Serve tacos immediately with the Guajillo salsa, thinly sliced Romaine lettuce, a lime wedge, and crumbled queso fresco, if desired.