Preheat oven to 450 degrees F. Line a rimmed baking sheet with parchment paper. 

Bring a large cast iron skillet to medium-high heat. Add 1 tablespoon oil. Swirl to coat the pan. Add garlic and move around pan until fragrant. Add onion and move around pan until softened. Add cooked, shredded chicken and taco seasoning. Stir to combine and continue to move chicken around until it's warmed through. Remove from heat. 

Add refried beans to a small saucepan and warm over medium heat, stirring as-needed. 

Wrap tortillas in a thin, clean kitchen towel. Place in microwave and warm. Keep warm while you assemble tacos. 

Taking the warmed tortillas one by one, rub a bit of olive oil over each side and then lay down on the parchment. Spread some refried beans on half (a thin layer), top with some shredded chicken mixture, and then some shredded cheese. Fold the other side over gently and top with a little more cheese. (The oil and warmth of the tortillas will help them from cracking, but some cracking is still normal!). Repeat with remaining tortillas.

Place in the oven, middle rack, to bake for approx. 10-15 minutes. Feel free to finish with 1-2 minutes under the broiler if you want - just watch very carefully. 

Serve with your favorite toppings.