Preheat and Prepare: Preheat the oven to 190°C. Lightly grease a 23x33 cm baking dish with oil or butter to prevent sticking and ensure easy serving later.

Prepare the Filling: In a skillet over medium heat, sauté the diced onion and minced garlic until softened and fragrant, about 3-4 minutes. Add the shredded chicken, ground cumin, salt, and black pepper. Stir well to combine all ingredients and heat through, allowing the spices to bloom and flavor the chicken mixture.

Soften the Tortillas: Quickly warm the corn tortillas either in a dry skillet for about 10 seconds per side or in the microwave for 20-30 seconds between damp paper towels. This step is crucial as it makes the tortillas pliable and prevents them from cracking when rolled.

Prepare the Base: Pour approximately 120 ml of the green chile sauce into the bottom of the prepared baking dish, spreading it evenly to create a flavorful base that will help prevent the enchiladas from sticking.

Assemble the Enchiladas: Take one warmed tortilla, add a generous spoonful of the chicken mixture down the center, and sprinkle with some of the Monterey Jack and cheddar cheeses. Roll the tortilla tightly and place seam-side down in the baking dish. Repeat with remaining tortillas, arranging them snugly in the dish.

Add Sauce and Cheese: Pour the remaining green chile sauce over the rolled enchiladas, ensuring they're completely covered to keep them moist during baking. Sprinkle the remaining Monterey Jack and cheddar cheeses evenly over the top for a golden, bubbly crust.

Bake: Place the uncovered dish in the preheated oven and bake for 25-30 minutes, until the cheese is melted and bubbly with light golden-brown edges. The sauce should be simmering around the edges of the dish.

Garnish and Serve: Remove from the oven and sprinkle with freshly chopped cilantro. Serve hot with optional sour cream on the side for added creaminess and to balance the heat of the chile sauce.