Heat a large saucepan and dry-fry the cumin seeds and chili flakes for 1 minute, or until they start to release their aromas.
Add the oil and onion, and cook for 5 minutes.
Stir in the lentils, stock and tomatoes, then bring to the boil. Simmer for 25-30 minutes until the lentils have softened.
Whizz the soup with a stick blender or in a food processor until it is a rough puree, pour back into the pan and add the chickpeas. Heat gently and season well.
Serve with small pieces of toasted bread and Parmesan shavings.