Chop each wing into 3 pieces. Fill a deep-fat fryer with half sunflower oil and half butter. Bring to 120°C. Add the wings and ‘fry’ until fully caramelised; this will take around 45 minutes. Remove the wings and pat dry on kitchen towel.
Place in a heavy-bottomed pan and cover with cold water. Bring to a gentle simmer and add the tomato purée. Simmer for 5 hours, skimming off any scum