I found the post below from Erika L in a few threads so I hope it's ok to just copy it here... I made this two days ago and it is still a little soft. (I wouldn't call it runny anymore, but is still softer than what I was looking for.)
One thread .(http://chowhound.chow.com/topics/851818) even had a question about the thickness, but the advice was just to leave it in the frig longer to set. I think mine's as set as it's going to get.
1. I'm considering adding more melted chocolate to see if that will make the final product a little thicker. Is that likely to work?
2. I put in 1 Tablespoon of chocolate liqueur for extra flavoring. Is 1 T too much?
I've also made Alton Brown's Moo-Less Chocolate Pie, and it came out too thick for what I'm looking for.
Here's the recipe from Erika L:
Trust me on this one--it makes THE smoothest, richest, creamiest, chocolatiest mousse ever. I just put it on the table and don't tell anyone what's in it, and no one's ever guessed when I asked. I don't know your definition of fluffy but nothing in this recipe gets air whipped into it.
3/4 c sugar
3/4 c water
1 pound silken tofu
8 oz chocolate--dark, dark sweet, bittersweet, semisweet, milk, whatever
flavoring: vanilla; cinnamon; rum; whatever
Bring the sugar and water to a boil and stir til the sugar dissolves; cool.
Melt the chocolate and let it cool a bit.
In a blender (don't try this with a mixer), buzz the sugar syrup, chocolate, and tofu till smooth, scraping down the sides at least once. Pour it into a serving dish, individual dishes, a pie shell, whatever, and put in the fridge til cold