Preheat oven to 375°.
In a saucepan add the olive oil and flour.
Whisk together and cook over medium heat for about 2 minutes.
In a bowl, combine chili powder, onion powder, garlic, cumin, salt and oregano.
Add to the roux, whisking together.
Next, add the chicken broth and tomato sauce.
Whisk and continue to cook for a few minutes until sauce is warmed and slightly thickened.
Stir in heavy whipping cream and remove from heat.
Cover the bottom of a baking pan with a bit of enchilada sauce.
Dip tortillas into enchilada sauce and place on a rimmed plate or pie plate.
Top with chopped brisket and shredded cheese.
Roll up and place seam side down into the baking dish.
Fill the dish and spoon additional sauce over the top of the enchiladas.
Top with remaining cheese.
Cover with foil and bake for 25 minutes.
Carefully, remove the foil and bake another 10- 15 minutes or until sauce is bubbly and cheese is melted.
Remove from oven and allow to rest 10 minutes before serving.
Serve enchiladas with desired toppings.