Heat the olive oil in a large pot over medium heat. Add the diced onion and sauté until softened, about 5 minutes.

Incorporate the minced garlic, ground cumin, ground coriander, ground cinnamon, ground ginger, cayenne pepper, and ground turmeric. Stir constantly and cook for 1-2 minutes until the mixture is fragrant.

Mix in the diced sweet potatoes, ensuring they are well coated with the spices. Continue to cook for 2-3 minutes, stirring occasionally.

Pour in the vegetable broth and add the diced tomatoes with their juices. Bring the mixture to a simmer, then reduce the heat to low, cover, and let it simmer for 15-20 minutes, or until the sweet potatoes are tender.

Once the sweet potatoes are tender, use an immersion blender to purée the soup directly in the pot until smooth. Alternatively, you can blend the soup in batches using a regular blender, then return it to the pot.

Stir in the chickpeas and season with salt and pepper to taste. Heat through to warm the chickpeas.

Ladle the soup into bowls, garnishing each with chopped cilantro. For added creaminess, swirl in a spoonful of Greek or coconut yogurt just before serving.