When I want to pull out all the stops with a chocolate dessert, I go for the flourless chocolate cake, since it's both as simple and rich as you can get. For the holidays, though, I like to dress it up with chestnuts, one of my favorite wintertime ingredients.
Chestnuts have a delicate, earthy flavor with a meaty texture. The classic way to prepare them is to buy them whole, score an "X" in the shell, roast them, and then painstakingly peel them, but the sore fingertips that you end up with can be a huge disincentive. Instead, I take a shortcut by purchasing chestnut purée, which saves a ton of preparation time. But there is a catch: canned chestnut flavor is mild compared to freshly roasted ones.
To compensate, I use slightly less chocolate in the torte than I otherwise would, so as not to completely overpower the chestnut flavor. I also add a bit of bourbon to enhance the delicate taste. These adjustments are enough to make the purée shine through.
After I make the torte, I squeeze some extra sweetened purée into a swirly mound on top, just like the classic Mont Blanc. I used a pastry bag for the one you see here, but I recommend using a potato ricer if you have one (I didn't): it will be easier and you'll get even finer spaghetti strands.
Depending on serving temperature, you'll get two different textures out of this cake. At room temperature it's luxuriously soft, like mousse. When chilled, it turns dense and fudgey, an equally enticing option. Either way, dust it with a touch of powdered sugar before serving for a final dose of class.