West African Peanut Butter Soup

1 tbsp olive oil
1 large onion, finely chopped
1 tbsp ginger grated
3 cloves garlic, crushed
5 cups vegetable broth
1 sweet potato, cubed
2 cups silver beet, shredded
1/2 cup tomato puree
1/2 cup Forty Thieves Peanut Butter
1 tsp ground cumin
1 tbsp chilli flakes
Salt and pepper to taste
Coriander and crushed peanuts to garnish