Pre-cook chicken and either shred or cube.
In the bottom of a crock pot, add cut up Velveeta cheese, can of Rotel tomatoes, cooked chicken, sour cream and taco seasoning and mix well.
Cover and heat on high for 45 minutes to 2 hours, mixing about every 20 minutes to avoid hot spots in the cheese.
About 15 minutes prior to serving, add can of drained and rinsed black beans and mix.
Continue cooking for 15 minutes to warm the beans.
Sprinkle nacho cheese with chopped green onions and serve warm with tortilla chips and any additional toppings.