Chicken can be both.- I prefer chicken to beef and pork. (uncountable)
- There are three chickens running around in my garden. (countable)
Chocolate is usually uncountable but can also be used as countable (esp. when small and wrapped). 
- I love chocolate. (uncountable)
- Life is like a box of chocolates: you never know what you �re going to get. (countable)
Yoghurt is uncountable.
- My favourite is coconut yoghurt. 
In spoken English, some people might use  �yoghurts � when they mean pots of yoghurt.