1
Mix lime zest and sour cream in a small bowl and refrigerate until ready to serve.
2
Saute onion and garlic in butter for 3 minutes.
3
Add sweet potatoes and chicken or vegetable broth and stir.
4
Season with cumin, chili flakes, and ginger.
5
Bring to a boil then simmer covered for 15 minutes until the sweet potatoes are very tender.
6
Puree all vegetables and return to a soup pot. Whisk in peanut butter, lime juice and salt. Heat soup.
7
To serve, ladle into soup bowl with a dollop of the sour cream/lime mixture. Sprinkle with diced tomatoes and cilantro. Optionally, also sprinkle in some more crushed red pepper flakes.