Preheat your oven to 375°F (190°C). This ensures the oven is at the right temperature when you're ready to bake the casserole.

Saute aromatics: In a large skillet, heat the teaspoon of olive oil over medium heat. Add the finely chopped onion and sauté for about 5 minutes, or until the onion becomes translucent and slightly golden. Stir occasionally to prevent burning.

Heat the chicken: Add the shredded chicken to the skillet with the onions. Sprinkle the taco seasoning over the chicken and mix well to ensure the seasoning is evenly distributed. Cook for an additional 2-3 minutes to allow the flavors to meld. Taste and adjust salt and pepper as needed.

Prepare the baking dish: In a 9x13 inch (23x33 cm) baking dish, spread a thin layer of enchilada sauce to cover the bottom. This prevents the tortillas from sticking and adds flavor to the bottom layer.

Roll the tortillas: Take a tortilla and spread about 2 tablespoons of red bean paste on one side. Add a portion of the chicken mixture on top of the bean paste. Roll the tortilla tightly and place it seam-side down in the baking dish. Repeat this process with the remaining tortillas, arranging them snugly in the dish.

Cover with sauce: Pour the remaining enchilada sauce over the rolled tortillas, ensuring they're evenly covered. This sauce will seep into the tortillas during baking, adding moisture and flavor.

Sprinkle the shredded mozzarella cheese evenly over the top of the casserole. The cheese will melt and create a delicious golden crust.

Bake: Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the cheese is melted and bubbly, and the edges of the tortillas are slightly crispy.

Let them rest: Once done, remove the casserole from the oven and let it rest for 5-10 minutes before serving. This resting period allows the layers to set, making it easier to serve and ensuring the flavors have time to meld together.

Serve hot, dividing the casserole into 8 equal portions. You can garnish with fresh cilantro, a dollop of Greek yogurt, or a squeeze of lime juice if desired.