Johnston worked for nineteen years as a curator at the
Auckland Art Gallery Toi o Tāmaki. Following the 2002 exhibition, 'Sir Edmund Hillary: Everest and Beyond', which she curated for
Auckland Museum, Johnston published her first book,
Sir Edmund Hillary: An Extraordinary Life. The book was translated into German by Ursula Pesch and Hans Freundl. Johnston collaborated with David Larsen to write
Reaching the Summit, biography of
Edmund Hillary for young adults. Johnston has published a number of books celebrating New Zealand's culinary history including
Ladies, a Plate (2008),
A Second Helping (2009), ''What's For Pudding?
(2011), and Ladies, a Plate: Jams and Preserves'' (2016). == Awards ==