Valls is a small town inland from Tarragona, about 50 kilometres south west of us. It's a sleepy little place, but it seems to have contributed three major elements of Catalan culture – it is considered to be the origin of castellers, of calçots, and of the Mossos d'Esquadra. I've already written about the castellers ( Castellers in the air ) , and the Mossos can wait, but let's consider calçots.

You eat calçots. It's a vegetable that looks like a leek, but isn't. We've asked several people – friends who cook enthusiastically, waiters – and the usual answer to the question 'What are calçots?' is something like 'calçots are calçots are calçots'. The best explanation is that it is a sort of stretched onion, because you grow them like this. You plant an onion and wait. When the first green shoots appear, you rake up earth around the sprouts and bury them, then wait again. When the green shoots struggle into sight once more, repeat the process, and wait again. And so on, until you have converted a round onion into a long, thinnish, pale green stalk with some dark green leaves on top. Then eat.

The eating of calçots is a whole impressive ritual. The first time we became aware of calçots was in a restaurant next to a tableful of impeccably besuited businessmen. As they chatted urbanely, waiters appeared and tied large baby-blue plastic bibs around their elegant necks. Could they really be such infantile eaters, we wondered … but then the calçots appeared, and we saw the point.

Calçots, cooked, are very messy. You cook calçots by charring them over a fire. You then heap dozens of them onto a terracotta roof tile, and serve, looking like the remains of a large garden bonfire. You pick up one of these carbonised leek-like things by the blackened green leaves, grip the other end firmly, and pull apart. If you have the knack, the charcoal outer covering slips away, leaving you with the fresh, clean, soft white interior. If you don't have the knack, you scatter black flakes and oil and calçot juice over everything in sight. Hence the bib – although for beginners I would recommend a full wetsuit, with goggles.

Then you get to the really messy bit. Calçots are usually eaten with xato, the classic sauce of the area around Tarragona, a pinkish creamy liquid based on hazelnuts and tomatoes and garlic and … oh, lots more things. You dunk the calçot in the xato, put your head back, raise the dripping calçot above your mouth, and slide home (see photo). Well, that's the theory – as you might imagine, aiming can be a bit of a problem. The descending calçot can go into your left eye, your right ear, or down your neck. But don't be discouraged, and remember that practice makes perfect – and there is plenty of practice to be done, because you have about two dozen more of the things to eat.

Actually, calçots are delicious. The flavour has something of the sweetness of cooked onions, but none of the slight tartness and acidity – and the xato adds a piquant touch. The texture is almost fruity: a slight fibrous firmness, but melting in the mouth. And over all the suggestive aroma of barbecue as a dark contrast …

The calçot season starts around November and runs to March. Restaurants start to hang out hand-written signs saying 'Hi ha calçots', and you ring up to reserve a couple of servings. Which is what we have done for tomorrow night at Can Llosas, a simple country restaurant up in the hills, where they really understand calçots ...

** See the page  Exploring calçots  which suggests several different ways in which this text can be exploited, and provides a handout of the text, with worksheet.