I found a recipe on the internet somewhere that is very good. I have modified it a bit and make it frequently. There is some in my frige nearly all the time.

4 Tablespoons butter - melt, take off heat
3 Tablespoons cocoa powder - mix into butter
few grains of salt (salt improves anything sweet)
Sugar substitute equal to about 1/2 cup

mix all this very well

1/2 teaspoon vanilla
3 Tablespoons heavy cream

again mix very well.

I add nuts, put it on a piece of plastic wrap on a plate and spread it out.
Cool and enjoy.

This needs to be kept in the frige as the base is butter and it gets the consistence of butter if left out at room temperature. We take it out of the frige, cut a piece and then put in back.

For the sugar substitute I use 1 tablespoon of Whey Low which is a sugar blend with 3 carbs per tablespoon (versus 12 for sugar) from wheylow.com plus 36 drops of a liquid Splenda product that I get from locarber.com. I find the combination tastes better than all Splenda and the total carbs are 3 versus 12 for 1/2 cup of granular Splenda.

If you add more cream to the recipe and leave it out of the refrigerator, it is a nice chocolate sauce.