I had issues with both girls from time to time, but the best thing that I have come accross is asking them "how many mouthfuls of X food do you think you need to eat to be finished" sort of giving them some control in their eating, where mummy and daddy get to choose just about everything else in their lives. Often the girls are so worked up in answering the question that they answer with a much bigger answer than you will be expecting.
Otherwise as a child, mum would put any left over dinner back in the fridge and that would be breakfast, I used to enjoy lasagne for breakfast. DD1 often will have left over cooked vegis as her fruit/vegi break for school because of this.