Put the ham hocks in a large pan with the stock ingredients. Cover with cold water. Set pan over a high heat and bring to the boil. Reduce heat to a simmer, cook for 2 and a half to 3 hrs or until the meat falls from the bone. Leave to cool in the pan. Save the stock.

Grease a 1-litre mould or tin with the oil, then line with cling film.

Tear the gammon from the bones and remove any skin or sinew that you don't want in your terrine. Chop or shred the gammon and mix with the mustard and parsley. Press it into the mould.

Bring the stock to the boil and reduce until you have around a pint left. Remove from the heat. Meanwhile, soak the gelatine in cold water for 5 mins to soften. Remove from the water and add to the stock, stirring until it's melted.

Cover the gammon with the stock and tap the tin to let out any air. Chill for 3-4 hrs or overnight. To serve, remove from the mould and cut into thick slices.