Butterscotch Cream Pie

I have been experimenting with butterscotch recently.  I had my heart set on a cream pie with a silken tofu base.  Sadly, the flavor was good with this but the texture was a little grainy.  I am not sure what I did but it was still edible but not nearly as good as I had hoped!

Has anyone else had issue with a tofu based pie coming out grainy?  Was it over cooked?  Thoughts?