icing
noun /ˈaɪsɪŋ/
  /ˈaɪsɪŋ/
 (especially British English) (North American English usually frosting)
 [uncountable]Idioms - a sweet mixture of sugar and water, milk, butter or egg white that is used to cover and decorate cakes
- Pipe a little green icing around the strawberries.
 - Roll out the icing into a large square.
 - Trim off excess icing around the base.
 
Oxford Collocations Dictionaryadjective- fondant
 - royal
 - chocolate
 - …
 
- cover something with
 - pipe
 - spread
 - …
 
- sugar
 - bag
 
 
Idioms 
the icing on the cake 
(North American English also the frosting on the cake)
- something extra and not essential that is added to an already good situation or experience and that makes it even better
- It’s an added bonus—the icing on the cake.