1. Sweat the diced red onion and garlic in a thick-based pan with the vegetable oil for ten minutes until softened.
2. Add the sweet potato and garam masala and cook for 2 minutes.
3. Stir the bouillon into the boiling water to make a stock then add to the onion mix.
4. Simmer for 5 minutes then add lentils and simmer for 5 more minutes.
5. Add all remaining ingredients except the spinach, bring to the boil, then simmer for 45 minutes.
6. Stir the spinach leaves through and serve.