In a bowl whisk together enchilada sauce and half & half. Set aside
In a large pan or skillet heat olive oil on medium high and add diced onion. Cook until translucent, about 5 minutes
Add ground beef, break it up and cook until fully browned
Add taco seasoning, salt, pepper and liquid. Turn heat to low and let cook another 3 minutes.
Mix in black beans and 1/3 cup of the enchilada sauce mixture. Turn heat to low and cook for another 1-2 minutes
Spread layer of enchilada sauce on bottom of a 2-3 quart casserole dish. Fill each tortilla with beef/bean mixture and a sprinkle of cheese. Fold and place seam side down in baking dish, lining up closely to each other
Pour remaining enchilada sauce over top, and sprinkle on remaining cheese
Bake for 20-25 minutes, until cheese is starting to bubble
Allow to cool for a few minutes before serving, garnished with green onion