Can you do goat products? Goat yogurt is a good sub.

Thanks guys. I'll keep you update on how it turns out...

Sour cream is normally used as a substitute for creme fraiche, so look for a non-dairy/vegan sour cream substitute. Just as thought. — Keep us posted on your results. :-)

Personally, I would alter the recipe to exclude the "creaming" of the leeks (I'd have to see the full recipe to give alternatives.) I try not to use overly processed foods (and soy is one of the most processed out there) in anything I cook or eat.

I would try soy yogurt for the texture/richness, then some lemon for the tanginess. I've also seen soy sour cream, but have never tried it.

It is for a creamed leek & smoky fish pie that I found in my low GI cookbook, it doesn't have potato on it so perfect for my low carb diet. I can swap the milk for Soya, but it is the creme fraiche that will cause the problems. It might not be possible but thought I would ask the question.

Maybe silken tofu?? Agree with the others, hard to say exactly, without knowing what you are making.

If you could share the recipe with us, maybe someone would have an idea. It's hard to know what to substitute otherwise.

I think it depends on what you're making. Creme fraiche imparts both a creamy silky richness and a tanginess that I think would be difficult to achieve in a substitute. If it's the main part of the dish, you should probably make something else. If it's an enhancer, you could add butter (clarified?) for richness; an acid (lemon juice, vinegar) for tanginess.