1. Peel the celeriac thickly, wash, cut into 3 cm x 6 cm sections and turn barrel-shape, keeping them in acidulated water to prevent discoloration.
2. Place into simmering blanc, and cook gently for 6 minutes.
3. Drain well, then toss in 75 g butter and season with salt and milled pepper.
Place 50 g flour into a basin, whisk in 2.5 litres cold water, then strain into a deep pan, add the juice of 2 lemons and salt and bring to the boil. The food, e.g. calfs' feet, Jerusalem artichokes, celeriac is added, normally covered with a muslin during cooking.