chocolate tart/pie using Regular/Icing sugar

Anyone got a chocolate tart/pie filling which uses either regular sugar or icing sugar?
I don't have any caster sugar (run out) , and I've already made the shortcrust base, it just needs some filling and the recipe I had requires caster sugar.
I don't want it to be really gritty which I suspect it would be if I used regular sugar.

TIA

This is a really good low fat North American chocolate pudding recipe that works well:

http://www.culinate.com/books/collections/all_books/Moosewood+Restaurant+Low-Fat+Favorites/Dark+Chocolate+Pudding

Thanks, I think that might be a bit smooth, I was thinking more tarte au chocolat

Anyway, annoyingly, after much looking around I couldn't really find one I liked the look of, and ended up making pioneer woman's peanut butter oreo pie instead

I got a pumpkin pie at wholefoods yesterday and made a Pecan, so hopefully guests will be full + happy.