Start by melting butter in a medium-sized saucepan over medium heat. Stir in the chili powder, garlic powder, onion powder, and cumin. Cooking the spices in butter for about a minute releases their flavors, filling your kitchen with an enticing aroma. Whisk in the cornstarch and cook for another minute to form a good base.
Slowly pour in the chicken stock while whisking consistently to prevent lumps. Follow up with tomato sauce, sugar, and salt. Simmer this mixture until it thickens into a luscious sauce, then set it aside to cool slightly.
While the sauce is cooking, grab a large mixing bowl. Combine the shredded chicken, 1 cup of cheddar cheese, sour cream, cilantro, and a quarter cup of the enchilada sauce. Mix everything until evenly combined. This filling should be creamy and flavorful, perfect for rolling into tortillas.
Preheat your oven to 350°F. Pour 1 cup of the prepared sauce into the bottom of your baking dish and spread it out evenly. Lay your tortillas flat, and spoon roughly ¼ cup of the filling into the center of each one. Roll the tortillas tightly and place them seam-side down in the dish. Repeat until all the filling is used.
Spoon the remaining enchilada sauce over the rolled tortillas, ensuring each is entirely coated in the flavorful sauce. Sprinkle the rest of the shredded cheddar cheese on top. The cheese will form the gooey, golden crown of your dish.
Pop the dish into your preheated oven and bake for 20-25 minutes, or until the cheese is melted and bubbly. Once out of the oven, let the enchiladas cool for about 10 minutes. Garnish with your favorite toppings and serve warm.