Kendal Mint Cake was one of the items — along with sturdy rope and a Metebelis crystal — that the Eleventh Doctor requested in his efforts to rescue Hila Tacorien from a pocket universe connected to Caliburn House (TV: Hide)
Behind the scenes
In reality, Kendal Mint Cake is a sort of energy bar from around the Lake District, which is frequently consumed by hikers. Thus, his request wasn't like his rather random food choices of Jammie Dodgers or fish custard in other episodes, but fairly logical given the circumstances.
Specifically, Kendal Mint Cakes come from Kendal, Cumbria's second city. Thus, the positive, even heroic, mention of the food counterbalanced the earlier sleight the script had given to Cumbria when Clara said that Carlisle was the "opposite of bliss".