Preheat the oven to 350 degrees F.
To make the sauce, melt the butter in a skillet or small saucepan over medium-low heat. Whisk in the cornstarch, and cook for 1 minute.
Stir in the chili powder, cumin, oregano, and salt, and cook until fragrant, about 30 seconds.
Slowly stream in the chicken stock, constantly whisking until everything is combined.
Stir in the tomato sauce and sugar. Cook until thickened, about 4-5 minutes.
Add ½ cup of the sauce to the bottom of a 9x13-inch baking dish, set aside.
In a large skillet over medium heat, brown the ground beef, breaking it up into crumbles until there is no pink left, then drain any excess grease.
Next, into the ground beef stir in the diced green chiles and taco seasoning until combined.
Then, stir ½ cup of the cheese until melted, remove from heat.
Spread about ¼ cup of the meat mixture down the center of a tortilla and sprinkle with about 1 tablespoon of the cheese. Roll it up tightly and place seam-side down into the prepared pan.
Repeat with the remaining tortillas and filling.
Spread the remaining sauce on top. Top with the remaining shredded cheese.
Cover with foil and bake for 30 minutes. Remove the foil and bake for an additional 5-10 minutes until bubbly.
Top with cilantro and serve with any additional toppings if you desire.