Blanch the corn in a large saucepan in 2 separate batches for 10 minutes. Drain well and pat dry on kitchen paper. Cook the cobs on a hot barbecue for 5—6 minutes, turning frequently, until evenly charred and tender.
Meanwhile, place the salt and chilli flakes in a mortar and pound with a pestle until the salt turns a rusty red.
Place the corn on plates and top with butter, sprinkle with the chilli salt and garnish with the lime wedges.