Heat oil in a large non-stick pan and saute the chorizo without oil until lightly browned and staining the oil red. Remove chorizo to a plate, keeping the oil in the pan
Add onion and potatoes and toss to coat with the oil and brown over medium-high heat. Add 1/2 cup (125 ml) water, cover the pan, reduce heat and steam-cook the potatoes for about 8 minutes
Add garlic, tomatoes, salt and pepper and chickpeas and return the chorizo. Bring to the boil, reduce heat, cover tightly and simmer for minutes, stirring occasionally
Stir in coriander and chilli, if using, and simmer a further 1-2 minutes