Heat the oil in a large pot over medium/high heat and cook for 8 - 10 minutes until caramelised.
Stir in the cardamom and cinnamon stick and saute for a minute before adding the ginger and garlic for 2 minutes.
Then add the red chilli powder, cumin powder, coriander powder, turmeric and garam masala. Cook for 2 minutes then add the passata. Bring to a simmer and cook for 10 minutes.
Stir in the lamb and cook for 10 minutes, stirring until fully combined. Add a splash of water if need be.
Add the peppers and potatoes. Cook for a further 10 minutes and add salt. Stir through and check seasoning. Serve with chapati.