2: Put in a large saucepan and add 1 litre whole milk, 1 bouquet garni and salt. Bring to the boil on medium heat, then turn the heat right down and leave to simmer, watching that the pan does not boil over.
3: Meanwhile, bring a pan of salted water to the boil and plunge 1 bunch parsley into it for 30 seconds to blanch.
4: Drain and cool under really cold running water.
5: Once the celeriac is soft...
6: ...take the pan off the heat and blend the contents.