To make the enchilada sauce, heat the oil in a large saucepan over a medium heat and cook the flour for about 1 min, stirring constantly. Add the chili powder, onion powder, garlic powder, cumin and 1 tsp salt, and fry for 2 mins. Add the chipotle, tomato paste and vinegar, and stir for another 1-2 mins. Pour in the stock and whisk until everything is combined and there are no lumps. Bring to the boil, then turn down the heat and simmer for 5 mins, or until thickened. Remove from heat and leave to cool.
