Sauté Aromatics (Optional): In a small pan, heat a teaspoon of oil. Sauté the chopped onion until softened (about 3 minutes). Add the minced garlic and cook for 1 minute until fragrant.
Mix Filling: In a large bowl, combine the mashed potatoes, roasted green chiles, 1/2 cup of shredded cheese, and the sautéed aromatics (if used).
Season: Add salt, pepper, and cumin. Mix well until everything is evenly combined. Taste and adjust seasoning as needed.
2. Prepare the Tortillas
Soften: Briefly warm the tortillas. You can either flash-fry them quickly in a little hot oil (a few seconds per side) to make them pliable and less likely to break, or wrap them in a damp paper towel and microwave for about 30-45 seconds. They must be flexible.
3. Assemble the Tacos
Fill: Take a softened tortilla. Place a spoonful of the potato and green chile mixture slightly off-center.
Add Cheese: Sprinkle a small amount of the extra shredded cheese over the potato mixture.
Fold: Fold the tortilla in half to form a half-moon shape (taco). Secure with a toothpick if necessary, though folding tightly usually works.
4. Fry the Tacos
Heat Oil: Pour oil into a deep skillet or frying pan until it is about 1 inch (2.5 cm) deep. Heat the oil to medium-high (around $350^\circ\text{F}$ or $175^\circ\text{C}$).
Fry: Carefully place 3-4 tacos into the hot oil. Fry for about 2-3 minutes per side, or until the tortillas are golden brown and crispy, and the cheese is melted and gooey.
Drain: Remove the tacos with tongs or a slotted spoon and place them on a plate lined with paper towels to drain excess oil. Remove any toothpicks if used.
5. Serve
Serve immediately with your favorite toppings such as sour cream, salsa, guacamole, or chopped lettuce.