Barbecue is both a type of food and an event. When speaking of the food, use the singular ("I love barbecue," by which you mean that you enjoy food that is prepared by barbecuing.) When speaking of the event (you are going to a barbecue), it would be correct to use the plural ("I like barbecues," by which you mean that you enjoy going to barbecue events).
"Pudding" is a non-countable noun. You would use the singular in most cases. However, if you are referring to two or more different types of pudding, it would be correct to say "I love mango and rice puddings."
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