Stir together the instant corn tortilla mix and baking powder in a medium sized bowl. Add enough water so that the masa is thick and firm.

Pour the vegetable oil into a large frying pan heating to 350°F/176°C. Divide the dough into 12-15 equal sized balls. Using a tortilla press, press each ball of dough into a thick tortilla. Carefully place the raw tortilla in the hot vegetable oil. The tortilla will sink to the bottom of the frying oil, but once it surfaces, flip the tortilla over. Allow to fry for another 45 seconds. Flip one more time and then fry for 20 more seconds.  The tortillas should puff as they fry. 

Using a slotted spoon or two spatulas, carefully remove the puffy taco shells from the vegetable oil, allowing the exceess vegetable oil to drain before removing from the pan. Place the shells in an oven proof pan lined with paper towels. Continue to press all of the dough balls and fry in this fashion. Serve immediately topped with your favorite taco toppings. Taco shells can be kept warm in an oven heated to 200°F (93°C)