Visitors to Barcelona this month are treated with a Catalan gastronomic treat, the Calçotada. A calçot is a large green vegetable belonging to the onion family, though it looks more like a leek with a green stem and white edible section. Eaten with a romesco sauce, they are absolutely delicious. There is only one way to prepare them to make the best of their flavour, and that is over a charcoal grill. At the table they are dipped in Romesco, composed of olive oil, hazel nuts, pine nuts, ...