Dr. Du Maurier, played by Gillian Anderson, says "but not today" much like Hannibal Lecter (Anthony Hopkins) did in The Silence of the Lambs (1991).
Following the pattern used in the previous seasons (to use as episode title terms relatives to a dish or a dish preparation - French cuisine in the first season and Japanese cuisine in the second) the third season use Italian nomenclature. Dolce (meaning "sweet") refers to a dessert course in Italian cuisine.