Hiya
I don't really use the soups but when I did I used a big mug, a novelty one which was huge! Then put the powder in, mixed it with some cold water until it was a runny paste, then add the hot water from the kettle slowly whilst stirring it. I still do this now with my hot shakes, but I usually split it into two now as I smashed my big mug by accident :'(.
Good look :-D xxx