Sweet Potato and Spinach Soup

I really liked this soup. It has a completely different flavor than most things I eat because of the peanut butter, soy sauce and ginger. I adapted this recipe from Robin Robertson's "Quick Fix Vegan." 

2 tsp. vegetable oil
1 yellow onion, chopped
1 large sweet potato, diced
1 TBS grated fresh ginger
2 tsp. ground coriander
1/4 tsp. cayenne pepper
1 (14-oz.) can diced tomatoes
2 TB. soy sauce
1/3 cup peanut butter
4 cups vegetable broth
Salt and freshly ground black pepper
1 1/2 cups milk (I used almond milk)
4 cups baby spinach
1/4 cup chopped peanuts (optional)

Heat the oil (or broth) in a large pot over medium heat. Add the onion and sweet potato. Cover and cook until softened, 5 minutes. Stir in the ginger, coriander, and 1/4 teaspoon cayenne or to taste. Add the tomatoes and soy sauce.

In a small bowl, combine, the peanut butter with 1 cup of the broth, stirring until smooth. Stir the peanut butter mixture into the soup, then add the remaining broth and season to taste with salt and pepper. Bring to a boil, reduce the heat to low, and simmer until the vegetables are tender, 10 to 15 minutes,

Stir in the nondairy milk and spinach and cook until the spinach is wilted, about 3 minutes. Serve hot, sprinkled with the chopped peanuts.