ENGLISH EXPRESSION: "ICING ON THE CAKE"
If you don't know, many birthday cakes in the UK are traditionally covered with "icing" which is basically solidified sugar. It is not very common in Spain, or at least I have not seen many Spanish cakes covered with "icing". "Icing" is especially popular for children because it can be very colourful.
So, essentially, icing is very popular in the UK but we also have an expression with "icing" which is "icing on the cake". This is used when you consider that something is great but something else has made it even better. For example: "Spain is amazing but the food is the icing on the cake".
Hope that helps!
Soy el director de Daniel Smith + Partners. Tengo más de 10 años de experiencia enseñando inglés a españoles.