Put water in soup pot. Boil potatoes until very soft. Using an immersion blender puree potatoes in soup pot.
Drain chickpeas, reserve liquid.
Add chickpeas to pureed potatoes and blend with immersion blender until very smooth or until desired texture is reached. You’ll likely need to add almost all of the chickpea liquid into the soup to facilitate blending and to adjust thickness of soup.
In a skillet sauce onions, garlic, salt, cumin, coriander, turmeric, cayenne and pepper until onions are translucent. Stir onion mixture into soup. Heat soup.
Add diced tomatoes and mint.Adjust seasonings.