Add the cornstarch, tomato paste and tomato sauce to a pot, whisk until well combined. Add to medium heat, stir in the chipotles, adobo sauce, garlic powder, onion powder, salt, cumin and stout.
Allow to simmer until slightly thickened, about five minutes.
In a small bowl mash together the avocados, salt and pepper.
Heat the tortillas slightly to make them more pliable.
One at a time spread tortillas with avocado, fill with black beans and corn, roll tightly.
Place into an 8X8 pan in a tight row.
Pour the sauce evenly over the pan.
Bake at 425 for 12-15 minutes or until warm and bubbly.