|Preheat the cast iron soup pot over medium heat. Add the chicken skin to render the fat and crisp it up, about 5 minutes.|
|Reduce the heat down to medium, then add the onions, carrots, and celery to the pot. Cook for about 5 minutes.|
|Add the garlic, mushrooms, and cumin and cook for about 1 minute.|
|Stir in the tomato paste, then add the chicken stock, bay leaf, and lentils. Bring to a boil then simmer for 45 minutes. Add more chicken stock at the end if the soup is too thick. Remove the bay leaves then pulse the immersion blender in the pot a few times.|
|Stir in red wine vinegar, then serve with tabasco, sour cream, tomato, and chives. Top with something crunchy for texture contrast.|
Leftovers keep well, but you might need to add some additional stock if the soup is too thick after reheating.