custard slice vs mille-feuille

custard slice

noun
  • Synonym of vanilla slice 

mille-feuille

noun
  • A type of pastry made of several layers of puff pastry usually filled with cream or custard, and topped with icing or sugar. 

How often have the words custard slice and mille-feuille occurred in a corpus of books? (source: Google Ngram Viewer )