Using a cleaver, bone the head by cutting an incision down the whole length of the skull from the forehead to the muzzle. Remove the tongue and split the skull in two, carefully removing the brain.
Soak the head (degorger) in cold water for 4 hours.
Once degorged, place the head in a saucepan with cold water to cover by at least 1 inch. Bring to a boil over medium–high heat, then lower the heat and simmer for 5 minutes. Drain well and refresh under cold running water.
Rub all surfaces with a cut lemon half before cooking dans un blanc.