Picksome of the custard mixture up and roll it into a ball between your hands. It feels slimy! If it is not mixed properly, you won't be able to do this.
Keep moving it - what happens if you stop? If you keep rolling it the custard forms a solid-seeming ball, but as soon as you stop....
...it runs away like a liquid. Yes, it is messy, but don't panic. When the mix dries out you can just brush the powder out.
