Chocolate filler (7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
fondant
(Other definitions for fondant that I've seen before include "Thick sugar paste used for icing cakes" , "Sugary paste for sweets" , "Sweet paste of sugar, water, and flavouring" , "Soft sweet" , "Thick creamy sugar paste" .)