Choose long, plump, firm roots with clean, black skin.

Wash, peel and coarsely grate or dice. Blanch dice in boiling water for 2 minutes, grated for 1 minute. Drain and 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: 3 months grated, 6 months diced.