Put a large pan over a medium heat for 1 min. Add 1 tbsp olive oil and the lamb. Fry for 5 mins, turning once or twice, till the lamb is browned all over.
While the lamb is browning, peel and finely slice the onion.
When the lamb is brown, lift it out of the pan and pop it in a bowl. Turn the heat down to low and add the onion with 1 bay leaf, 1 cinnamon stick and a splash of water. Season with salt and pepper. Gently cook for 5 mins till the onion is soft and golden. If it starts to stick, add a splash more water.
While the onion cooks, peel and crush or grate the garlic. Halve the chilli, scooping out the seeds and white bits. Finely chop it. Finely chop the coriander stalks (keep the leaves for later). Peel and roughly chop the potatoes. Roughly chop the courgette.
Stir the garlic, chilli and coriander stalks into the onion. Add the lamb back into the pan with any juices from the plate. Add the potatoes and courgette.
Pour in the chopped tomatoes. Half fill the can with warm water (around 200ml) and add to the pan. Crumble in the stock cube and add 1 tsp of the sugar. Cover, turn up the heat and bring to the boil.
Turn the heat down to medium. Simmer the stew for 25-30 mins till the lamb and potatoes are tender and cooked through. If it gets a little too thick, add more water. Taste and add more salt, pepper or sugar if you think it needs it. Serve the lamb bredie in warm bowls, garnished with the coriander leaves.