Preheat oven to 200 degrees. Set a wire rack over a rimmed baking sheet lined with foil for easy cleanup.
In a large skillet over medium-high heat, add about 1/2 inch vegetable oil and heat to 350 degrees. Add one tortilla to the skillet and cook until it is blistering but still soft, 10 to 15 seconds. Using tongs, turn tortilla over and then immediately fold to form a taco shell.
Once the tortilla is holding its shape, turn until crisp and golden all over, 15 to 30 seconds longer. Transfer to wire rack and keep warm in oven while repeating with remaining tortillas.
Best oil for frying: If you are frying corn tortillas, corn oil is the best choice. You can also use basic vegetable oil, peanut oil, soybean oil, safflower oil, or sunflower seed oil. You want a neutral-flavored oil with a high smoke point.
Make sure the oil is hot enough. Use a thermometer to gauge the temperature of the oil accurately. If you don’t have one, wet the tip of your finger with water and drip just one drop of water into the oil. If it sputters and crackles, the oil is ready.
But not too hot. Cooking with oil can be tricky. If the oil starts smoking, that means you’ve passed the point and should let the oil cool down a bit.
Don’t crowd the pot. Too many chips or tortillas in the oil cools the oil down and prevents things from getting super crispy. It’s better to work slowly than rush.
Add more oil as you go. Depending on how many tortillas you’re cooking, you may need to add more oil. Just let the oil heat up again before adding more tortillas.
Paper towels are your friend. Paper towels really soak up extra oil (and extra calories) so feel free to break them out. When I make chips, I’ll layer them between batches of fried chips as I work. Not into paper towels? I keep a stack of clean wash clothes in my kitchen in my kitchen just for situations like this. Use them, then wash them!
Seasoning and salt. Once the tortillas are crispy, salt and season them while they’re still warm. Use a coarse salt or any other seasoning you like. A sprinkle of chili seasoning, a squirt of lime juice, or maybe even a dusting of homemade fajita seasoning.
Shelf life: Use what you make right away, or all your hard work may become chewy (humidity causes the chewiness). You can store them in a paper bag folded over and kept out at room temperature. Leftovers can be reheated in the oven to crisp them up again.