With an immersion mixer or blender, puree the other can of black beans until smooth. Mix into the vegetable mixture (this adds thickness). Bring ingredients to a boil. Reduce heat to low. Add spices, salt and pepper. Stir in vinegar. Cook on low 20 minutes. Taste and add more vinegar or salt and pepper to adjust for personal taste.
Garnish with Cheddar cheese and sour cream to serve. (optional)