Tip the potatoes into a pan, cover with cold salted water, bring to the boil, then simmer for 10-12 mins until just tender. Drain well and leave to cool. Will keep chilled for 24 hours.

When your barbecue is hot, toss the spring onions in the olive oil and season. Place directly on the barbecue over a high heat and cook for 2-3 mins, turning until softened and charred. Leave until cool enough to handle, then finely chop and set aside. Heat a large barbecue-proof frying pan or roasting tin over direct heat. Add the butter until foaming, then toss in the potatoes, season well and cook for 10 mins, shaking the pan occasionally.

To give the potatoes a smoky flavour, add some wood chips to the embers and close the lid of the barbecue as the potatoes cook. Stir through the charred spring onions and cook for a final 5 mins. Tip into a large bowl and serve.