Mango Yoghurt

This particular 8-yr-old boy is usually really good (ie focused) for about 20 minutes, sometimes 25... and then he starts to get a bit silly, and in recent weeks has ended the lesson talking in a made up language (of which I think there are 3 in his repertoire).  Today he walked into the lesson talking in a made up language, and he didn't switch to his focused self for very long at a time.  By the time he was packing up, I realised what I should have asked at the beginning.

Me [lightbulb]: Ah - what did you have for afternoon tea?
Boy [mumbles]
Me: Chocolate?  Is that what you said?  You had chocolate for afternoon tea?  That explains a lot...
Boy: No... Yoghurt.
Me: Yummmm.
Boy: Mango yoghurt.
Me: Double yum!
Boy: .... aaaannnnd ... I had a lot of it...