Finely chop the onion and garlic.
Peel then cut the sweet potatoes and carrots into bite-sized chunks.
Heat the oil in a large saucepan and gently sauté the chopped onion and garlic until soft.
Add the spices and sweet potatoes, then stir for a minute to coat them well. Add the carrots, passata and enough water to cover the vegetables well. Add the bay leaf and the stock pot.
Bring to the boil, turn down the heat and simmer for 15 minutes under cover, until the sweet potatoes are tender and you get a thick stew.
Add the broad beans and cook for another 5 minutes or so.
Season to taste, discard the bay leaf, then serve with coriander leaves scattered on top.