Ox Tongue in Jelly

• cured ox tongue, weighing about 3½–4 lb (1.6–1.8 kg)
• 1 onion

Soak the tongue overnight in a saucepan of cold water. Bring slowly to the boil, draw off the heat and drain. (This helps to get rid of the excess salt.) Pour over fresh cold water to cover. Peel the onion and push the cloves into the onion. Peel and slice the carrots. Add onion and carrots to the pan along with the bay leaf. Bring to the boil, then lower the heat, cover with a pan lid, and sim