Select firm white bulbs, with fresh, green feathery leaves. Avoid any that are limp or discoloured.

Trim off the green fronds and chop finely. Scrape the outer white stalks, to remove the strings. Trim the base, then cut each head in quarters lengthways.

Fronds: Place in a rigid container, remove the air, seal, label and freeze. Storage time: 6 months.

Heads: Blanch the quarters in boiling water for 3 minutes. 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: 6 months.