fruit singular/plural

Question

This was fun, made me hungry. 
Why are the fruit in : "les sorbets au citron et à la fraise" singular, while in the pie "aux framboises" they are plural?

Céline Pickard · Accepted Answer

Bonjour Lorraine,
What a wonderful question! I am hungry too now. Here is the general view on it:
‘Sorbet au / à là + singulier’ 
because it is a general flavour and the appearance of the fruit has completely changed.
‘tarte aux + pluriel’
 because it is assumed that the fruits are accountable and can still be seen (their aspect hasn’t changed too much).
However, it is not a strict universal rule. The grammarians don’t always agree with one another either.
I hope this is helpful.
Bonne journée!

Gregory McClure · Answer

I was wondering the same thing.