Spicy Sweet Potato Soup

Here is a simple version of a recipe for Spicy Sweet Potato Soup - posted on the Food TV website.

But I like the Micahel Fagan version, suggested by Liz, as follows:
1/2 cup sour cream or creme fraiche
1 tsp grated lime zest
1 large plum tomato
1.5 to 2 lbs sweet potato
1 tbsp butter
1 onion, sliced
2 large garlic cloves, sliced
4 cups chicken stock
1/2 tsp ground cumin
1/4 tsp crushed chilies
2 tbsp grated fresh ginger
1/4 cup crunchy or creamy peanut butter
1 lime
2 tbsps chopped fresh coriander /parsley

I have a copy of the entire recipe