Prepare the Chicken: If using uncooked chicken, place the breasts in a saucepan and cover with water. Bring to a boil, then reduce the heat and simmer for 15-20 minutes, or until cooked through. Remove the chicken, let it cool slightly, then shred it using two forks. (You can skip this step if using pre-cooked chicken).

Sauté the Aromatics: Heat the olive oil in a large frying pan over medium heat. Add the chopped onion and cook for 5-7 minutes, until soft and translucent. Add the minced garlic and cook for another minute until fragrant.

Create the Filling: Add the shredded chicken to the pan with the onions and garlic. Sprinkle over the cumin, oregano, salt, and pepper. Stir everything together until the chicken is well-coated and heated through. Set the filling aside.

Make the White Sauce: In a medium saucepan, melt the butter over medium heat. Whisk in the plain flour and cook for 1-2 minutes, stirring constantly, to form a roux. This step cooks out the raw flour taste.

Thicken the Sauce: Gradually pour in the chicken stock while whisking continuously to prevent lumps. Bring the mixture to a gentle simmer and continue to cook for 3-5 minutes, until the sauce has thickened enough to coat the back of a spoon.

Finish the Creamy Sauce: Remove the saucepan from the heat. Let it cool for a minute, then stir in the soured cream, drained green chillies, and salt. Stir until the sauce is smooth and creamy. Taste and adjust seasoning if needed.

Assemble the Enchiladas: Preheat your oven to 180°C (160°C fan). Spread a thin layer of the white sauce (about 1/4 of it) over the bottom of a 23x33cm (9x13 inch) baking dish. What works best for me is to dip each tortilla briefly into the remaining sauce to soften it, which makes it easier to roll without cracking.

Fill and Roll: Place a line of the chicken filling down the centre of a sauce-coated tortilla. Roll it up snugly and place it seam-side down in the prepared baking dish. Repeat with the remaining tortillas and filling, arranging them in a single layer.

Top and Bake: Pour the rest of the white sauce evenly over the rolled enchiladas. Sprinkle the grated Monterey Jack and cheddar cheese over the top. Bake for 20-25 minutes, or until the sauce is bubbling and the cheese is golden brown and melted.

Rest and Garnish: Let the enchiladas rest for 5-10 minutes before serving. This allows the sauce to set slightly. Garnish with fresh coriander and sliced spring onions, if desired.