Don't put ice in it. I just use 150ml of cool water (let the cold tap run for a bit) then pour it over the already mixed powders. Blend for about 2 minutes then pour it into a bowl and place it in the freezer (find it sets better!) for 10-15 minutes depending on how set you want it to be, I personally like it slightly runny in the middle so put it in for 11 minutes (ok I have a little case of OCD when it comes to times! lol).
Enjoy.