About a month or so ago, Habanera (my boyfriend's mother, who is also gluten and dairy free) made Emeril Lagasse's New England Clam Chowder. Substituting the butter for margarine was an easy fix, but for the heavy cream it called for she went to Go Dairy Free. They have a very, very helpful page of substitutes.
Their suggestion for replacing heavy cream is to buy silken tofu and blend it in a food processor until it has the constitency of heavy whipping cream. She used this in the Clam Chowder, and it was by far the best clam chowder I have ever tasted (and I love Clam Chowder!). Since then, I have tried it myself and have been very pleased at how well it translates with dishes.
But for baking, I wanted it to taste more like actual cream. So I got the idea to add Silk Creamers, since they have a similar taste but not the consistency. Combining the two was a great success. I admit it doesn't smell very attractive, but try to direct your head away from your food processor when trying your mixture.
My recommendation is to find a blend between the silken tofu and Silk Creamer. This way, you can reach a taste that you personally like. But for now, here is my recipe. I blend it all at once and then store it in Tupperware in the refrigerator for further use.
Cream Tofu (Dairy Free Heavy Cream)
1/2 cup and 2 tbsp. (10 tbsp. total) Silk Creamer
1/3 cup French Vanilla Silk Creamer
1 tbsp. Sugar
1 package Silken Tofu
Blend all ingredients in a food processor until completely blended. Add more or less creamer and sugar to taste. Pour into desired dishes and enjoy.