Flavouring is something which is added to food to make it taste a certain way. Flavour is the way a food tastes. For example the cake had a lovely fruity flavour. In British English it is spelled flavour. In American English it is spelled flavor.

Flavoring is something you put in your food, like a spice or condiment. Flavor is the actual taste or description of that taste. e.g. flavoring gives your food flavor I think you can spell it both ways depending on whether you are using US or British English :)