Combine the stock, onion, garlic, and sweet potato in a stockpot and bring to a boil. Reduce the heat to a simmer and add the chicken, then cover and simmer for 20 minutes.
In a small bowl, whisk together the Barney Butter and 1/2 cup of the soup mixture into a thick paste. Add the collard leaves and ginger to the soup and bring to a boil, then reduce the heat and simmer, covered, for 5 minutes. Stir in the almond butter paste. Season with salt and pepper.
Ladle the soup into bowls. Scatter some fresh herbs on top, if you wish, and serve with lime wedges.