Pre heat oven to 400℉. Using a pastry brush, brush one tablespoon of olive oil over the inside bottom of a small baking sheet.
Line the prepared baking sheet with 6 of the tortilla shells. The shells should be hanging about 2 inches over the baking sheet. There should be no open gaps between the tortilla shells.
Rinse and cut tomato and pat dry with a paper towel. Rinse shredded lettuce and either pat dry with paper towel or using a salad spinner to remove all the water. This will prevent the tomato and lettuce from becoming soggy when cooked in the oven. Set aside.
Chop chives and set aside.
Slice chicken into thin pieces and set aside.
In a large saucepan over medium heat, heat 1 tablespoon olive oil. Add the chicken and cook on medium-high heat until completely done. (165 degrees) This should only take about 5 minutes since the chicken is very thinly sliced. Once the chicken is fully cooked add in the taco seasoning and water. Mix until the chicken is fully covered with the seasoning.
Using a large spoon, spoon the chicken over the tortillas evenly.
Evenly top the chicken with the cut tomato and shredded lettuce. Lastly sprinkle the shredded cheese over the top of the tacos.
Use the other 6 tortilla shells and place them over lapping on top and in the center. Fold the overlapping tortillas over the top to enclose the filling.
Using a pastry brush, brush the remaining olive oil over the top of the tortilla shells. This will help the over lapping pieces stick together.
Using a bowl press down on the tacos to help the tortillas stick together. This will create a sealed sheet pan taco.
Place the baking sheet in the oven and bake for 20 minutes. Remove the baking sheet and cover with aluminum foil and bake for another 15 minutes or until the tortillas are golden and crispy.
Let cool for 5 minutes before slicing. Garnish with your favorite toppings and enjoy!