Instructions:
- Cook the Chicken: Place chicken, 3 cups of broth, onion, smashed garlic, and 1 tsp salt in a saucepan. Bring to a boil, then reduce heat, cover, and simmer until chicken registers 165°F (74°C), about 18–20 minutes. Remove chicken; shred finely. Reserve the cooking liquid.
- Roast the Sauce Vegetables: Preheat broiler. Toss tomatillos, jalapeño, and unpeeled garlic cloves onto a baking sheet. Broil, turning occasionally, until skins are blackened and blistered (about 8–10 minutes).
- Prepare the Tomatillo Sauce: Peel the roasted garlic. Combine roasted vegetables, fresh cilantro, cumin, and 1 cup of reserved chicken broth in a blender. Blend until completely smooth.
- Finish the Sauce: In a clean saucepan, melt the butter over medium heat. Whisk in the flour to create a roux and cook for 1 minute. Slowly whisk in the blended tomatillo mixture until smooth. Bring to a gentle simmer. Stir in the crema/sour cream. Season with salt and pepper and keep warm.
- Soften Tortillas: Heat oil in a small skillet over medium heat. Quickly dip each tortilla (about 10 seconds per side) until pliable but not crispy. Drain briefly on paper towels.
- Assemble the Enchiladas: Preheat oven to 375°F (190°C). Spread a thin layer of sauce across the bottom of a 9x13 inch baking dish. Dip each softened tortilla briefly into the remaining sauce to coat lightly. Lay a tortilla flat, place a line of shredded chicken down the centre, sprinkle lightly with about 1/2 cup of cheese, and roll tightly. Place seam-side down in the dish.
- Bake and Serve: Pour the remaining sauce evenly over the rolled enchiladas. Sprinkle the remaining cheese generously over the top. Bake for 20–25 minutes, or until the sauce is bubbling vigorously. Let rest for 5 minutes before serving.