Select firm, round roots with as few knobbles as possible, for easy preparation.

Peel, halve, then coarsely grate or cut into thick slices or large dice.

Blanch in boiling water to which 15 ml/1 tbsp lemon juice has been added, for 3 minutes for slices or dice, 1 minute for grated. Drain, then plunge immediately in a bowl of iced water to cool. Drain again and dry on kitchen paper. Pack in convenient quantities in polythene bags, remove the air, seal, label and freeze. Storage time: 12 months.