For this or any other recipe, you want to prep your cardoons. They need to be properly trimmed of their leaves, which grow from the top and edges of the stalks, then cut into lengths, scraped on their outer sides to remove the fibrous ribs and hard green skin. (It helps to split them in half lengthwise so they lay flat on your cutting surface.) Like artichokes, they should be immediately submerged in acidulated water to prevent them from discoloring. They then should be simmered in salted water for about an hour (or 15 minutes under pressure) until they are quite tender. You are then ready to use them in a variety of ways.