Blackstone - Just make it with water. I made it tonight with only water, and in all honesty, it was still good - just slightly less "rich". Remember that you're adding all that tuna and the sweetness of the pepper, so the cream isn't significant. I just add it to dilute the mayo so it's not too sickly. I'm not sure about the sour cream, though - it would change the taste. You could try making a tiny bit of the curry dressing with the soured cream, and if you don't like it then just make it with water. It would be fine with milk too, but that's not Atkins-friendly.