A typical chocolate mud cake is packed full of sweet chocolate, powdered sugar, granulated sugar, lots of butter and eggs- the usual cake ingredients.  After perusing through a few recipes at www.cooks.com a few things became evident.

First the link below enlightened me to the very mundane and traditional recipe for Chocolate Mud Cake.  I'm sure that it tastes fantastic, but where's the imagination?  This recipe calls for butter, sugar, eggs, vanilla, and flour for the cake itself and unsweetened cocoa, powdered sugar, butter again, milk and pecans for the frosting.

http://www.cooks.com/rec/view/0,166,148190-230197,00.html

Another link from the same website had similar ingredients; yet, it was much more simple. It only required butter, semi-sweet chocolate chips, unsweeteded chocolate, sugar, DARK RUM, vanilla, and eggs. 

I finally found a tip at: http://www.flickr.com/photos/22876486@N08/2192634448/ .  This is for a bitter chocolate cake.

After compiling the best ingredients from these three sources I believe that to make the perfect "Bittersweet" Chocolate Mud Cake the following ingredients must be used:

• 1 cup of softened butter
• 4 eggs
• 1 tsp. vanilla
• 1/3 cup unsweetened cocoa
• 1/4 cup dark rum
• 1/3 cup Hershey's unsweetened cocoa
• 1 _^1/2 cups flour
• 2 cups granulated sugar
• 3 _1/2 ounces hot coffee

The rum will create a bittersweet taste, while the coffee will give you that bitter flavor you crave.  The ingredients listed above are for the cake itself, not the frosting.  After this is all mixed together, starting with the flour, cocoa, and eggs first of course, put mixture in a 9x13 inch baking pan with plenty of cooking spray so the cake does not stick to the pan.  Preheat the oven to 350 degrees fahrenheit and bake for approximately 25 minutes or until a toothpick comes out clean when inserted into the middle of the cake.

For the frosting use first recipe from cooks.com which is:

• 1/3 cups unsweetened cocoa
• 3 cups powdered sugar
• 1/2 cup melted butter
• 5 tbsp milk and
  
• 1/2 cup chopped pecans if desired

Combine the dry ingredients minus the pecans and add the butter and milk. Stir.  To make the frosting more bitter as per the theme of this recipe add 2 tbsp of the Dark Rum from earlier and 2 tbsp of dark hot coffee.

Another final method for making your cake more bitter is to add dark chocolate with 70% cocao or more to the mix.

I hope this recipe was helpful.  It sounds tasty enough that I may have to bake myself one today!