Preheat oven to 200°C. Fill a large saucepan with water to cover the potatoes, add the salt and bring to the boil. When the water starts boiling, cook for a further 5 minutes then drain the potatoes. Place the potatoes into a mixing bowl with the Simon Gault Mexican seasoning and oil, mix well until the potatoes are evenly coated. Place the potatoes in a single even layer in an ovenproof baking dish and bake for 25 minutes. Remove the potatoes from the oven and sprinkle the chorizo, grated cheese and return to the oven and cook for a further 5 minutes until the cheese has melted. Remove from the oven and allow to cool slightly. Sprinkle with the chopped chives and serve with a bowl of sour cream.