I'm not exactly sure how it goes, but it always starts out "Patty-Cake, Patty-Cake, Baker Man, Bake me a cake as fast as you can..."
Anyway, Grandma has been playing with Jack getting him to do patty cake, lately. She has been doing this a lot lately, so its no surprise that Jack has started to play along.
He is so smart - all you have to do is say patty cake and he puts his hands together, like a little clap, but with his hands closed. So cute.
He hasn't done the "roll em up", or the "toss it in the oven", but he probably will figure out that soon enough.