Salmon & Sweet Potato Chowder

• 15 g/½ oz butter
• 1 tbsp sunflower oil

Heat the butter and oil in a large frying pan over a high heat. Reduce the heat to medium, add the celery and onion and fry, stirring, for 3–5 minutes until the onion is softened. Sprinkle over the flour and stir for 2 minutes to cook out the raw flavour. Pour over the stock and bring to the boil, stirring continuously to prevent lumps from forming. The mixture will be very thick and paste-like