In a large soup pot or Dutch oven, melt butter over medium heat. Add onion and cook about 4 minutes until softened. Add garlic and cook 1 minute more.
Stir in black beans, corn, Rotel, fire roasted tomatoes, and taco seasoning.
Add chicken broth. Bring to a medium-high simmer and simmer for 5 minutes until hot.
Reduce heat to low. Stir in heavy cream, shredded chicken, and pinch cinnamon. Season to taste.
Ladle into bowls and garnish as desired.
Notes
Turn heat to low before adding heavy cream. This prevents curdling.
Use heavy cream, half & half or whole milk. Cream/milk with a higher fat content is less likely to curdle when put against heat.
You can use cream cheese or sour cream instead of or with the heavy cream. If using sour cream, mix a bit with heavy cream, water, or broth before adding it to the soup. If adding cream cheese, let it soften before adding, then stir until melted.
Store leftovers in an airtight container in the fridge for up to 3 days.
Reheat over medium low heat on the stove-top, adding broth as needed.