Preheat oil in saucepan, about 7 minutes. Ensure that oil is hot enough by sticking the end of a wooden spoon into the oil. If you see bubbles form around the wood and they start to float up, your oil is hot enough to cook with.
Place tortilla on slotted spoon, and then bottom-side of jar on top of tortilla. Lower into the pan of hot oil. Remove spoon carefully, making sure not to tear the tortilla. Use spoon around edges of jar to mould the tortilla around the jar. Keep for roughly one minute in the oil, and then use tongs to remove tortilla from pan and tilt to empty oil back into the pan. Lay on a paper towel-lined plate to drain and cool.
Fill with desired fillings, such as ice cream or taco salad.