Peel and finely chop the onion and garlic, dice the potatoes, finely shred the kale or cavolo nero, and slice the chorizo. Heat 4 tablespoons of oil in a saucepan over medium heat and fry the onion and garlic for 5 minutes, or till they begin to soften. Stir in the potatoes, season with sea salt, and cook for a further 5 minutes. Add 1.25 litres water and simmer for 20 minutes, or until the potatoes are soft. Mash the potatoes into the liquid to produce a smooth purée. Add the kale and simmer for 5 minutes. Heat 1 tablespoon of oil in a frying pan over medium heat and fry the chorizo slices, sprinkling paprika over them in the pan, for 3 to 4 minutes. Add the chorizo to the soup, then ladle the soup into bowls and season with freshly ground black pepper. Delicious served with a swirl of oil in each bowl and slices of corn bread.