Bonjour Tecla,

Nous dégustons des chocolats chauds

→ we’re having more than one hot chocolate each

Nous dégustons un chocolat chaud

→ we’re having only one each

 

Nous dégustons des gâteaux

→ we’re having more than one cake (there are several cakes to eat from)

Nous dégustons un gâteau

→ we’re eating from one cake together

 

I hope this is helpful.

Bonne journée !