Divide each thistle stalk lengthways into 6 cm (2½ in) pieces. As you finish cutting them, soak the stalks in water mixed with the juice of half a lemon to avoid discolouration. Leave aside until you are ready to cook them.
Drain, put them into a saucepan and cover with cold water. Add a little salt and bring to the boil. You can cover the surface of the thistle in the saucepan with a c