How to get an older child to write more...

There is an older 4 year old boy in class who is not a big writer. He is very interested in dragons. So today, he came up to me and asked me "Do we have an animal book making work?" Well at the moment we don't, unfortunately - because this would be a great opportunity for him to write. A little later he asked me again. I had recently bought a children's picture dictionary for those times when a child asks "How do you draw a ..." or when they want to know more about something. So I gave that to him so that he could at least look up a dragon and see the picture. He decided to make a 'parts of the dragon' book. He got bunches of paper and pencils and proceeded to draw a dragon. We then talked about how, if he's making a 'parts-of' book that he needed to make more pages for each of the parts. He made the head on one page, and the body on another. He started to write the words head and body on his two pages, by listening to the sounds phonetically. He wanted to keep going but unfortunately it was our outside time so he decided to save his work. It's amazing how going with their interests can really spark something inside of the child. Sometimes it might not be something we consider "appropriate" or "Montessori" but I would bet Maria Montessori would feel that following the child is more important in these instances. I forgot to take a picture of his work, will try and do that on Monday to post!