Rehydrate the two dried red chillies in a pan of boiling water for 20 to 30 minutes. Remove from the water and allow to cool until needed.
Meanwhile, heat a generous amount of olive oil in a casserole dish or saucepan. Add the green capsicum, onions and leeks, then cook until soft and translucent.
Add the head of garlic and the red chilli. Stir and cook for a minute then add the chorizo, potatoes, salt and water to cover.
Simmer until the potatoes are soft, about 25 minutes (or 5 minutes under pressure in a pressure cooker). Remove the garlic and dried chilli. Discard the dried chilli, but reserve the garlic.
Open the red chillies and scrape out the flesh. Remove 3 cloves from the head of garlic. Make a paste with the red chilli and garlic, mashing with a fork. Add this paste to the stew and cook for a further 5 minutes.