Ana found a good video in the Spanish newspaper ABC on how to make this Catalan specialty. (If you don't understand Spanish, don't worry: the images make the process, which is simple, clear.)
Basically you just grill the biggest green onions you can find until they're charred on the outside. Take them off the grill, wrap them up in paper or foil and let them steam five or ten minutes, then peel off the charred outer layer and enjoy them dipped in a good olive oil or romesco sauce (my easy romesco works well). The hot taste of the onion becomes sweet and rich during the cooking, and the texture is tender.
At the end of the video there is an example of the traditional way to eat these grilled onions (not with a knife and fork!)






