Here's how I did it:
I adapted the recipe on the back of the Hershey Dark Chocolate Cocoa can. I replaced the sugar with a low carb sugar blend and the flour with Lite White Flour blend from Big Skies Farm(www.bigskiesfarm.com). I used sugar free cherry pie filling on the top and frosted the cake with whipped cream to which I added about a tablespoon of sugar free vanilla pudding mix. It helps to stabilize the whipped cream and to sweeten it.
Low Carb Sugar Blend:
This recipe was developed by Scott123 at Low Carb Friends and will replace 1 cup sugar
5 Tablespoons Splenda
3 Tablespoons granulated erythritol
2 Tablespoons Whey Low
2/3 cup polydextrose
I have used this with great success in my recipes. I am not sure of the exact carb count but it is much lower than sugar!:) Splenda alone will not sweeten chocolate.Whey Low is available at www.wheylow.com and both erythritol and polydextrose can be obtained from www.honeyvillegrain.com.
Also my new favorite cookbook is "Carb Wars: Sugar is the New Fat" by Judy Barnes Baker. It has great recipes!