Select firm stems with a good, bright colour (green or purple and white). Avoid any that are flabby, wilted or slimy.

Sort into thin and thick stalks. Trim the base of the stems if woody and scrape thick stalks.

Blanch in boiling water for 1 minute (sprue or very thin stalks), 2 minutes (medium stalks), 3 minutes (thick stalks). Drain in a colander and plunge in a bowl of iced water to cool. Drain again and dry on kitchen paper. Tie in small bundles and pack in polythene bags. Remove the air, seal, label and freeze. Storage time: 12 months.