Poor Mark has had to bear with four permutations of this cake, but I think I've finally got the details ironed out.  It's delightfully simple, richly chocolate, and makes its own frosting all in the same pan.

First, preheat the oven to 350 degrees and pull out a glass, 9x13-inch cake pan (or two 8x8-inch square or two 9-inch round cake pans).  Now prepare the frosting:

• 1 cup of dark chocolate chips
• 0.5 cups of heavy cream
  
• 1 cup of jam.  (Blackberry or raspberry stands up to the chocolate best, but it wasn't bad with blueberry, and I might try strawberry next.  Homemade, low-sugar jams keep this from turning sickly sweet.)

Melt the chocolate chips in the microwave, being careful not to burn them.  (If you start with cold chocolate chips, it might take two minutes, but start with one minute since that will usually melt room-temperature chips.)  Next, stir in the cream and jam.  Spread the frosting mixture in the bottom of your pan.  (No grease is necessary in glass, but I'm not sure about metal.)

Now, make the cake:

• 5.5 tablespoons butter
  
• 0.75 cups brown sugar
• 2 eggs
• 0.5 cups yogurt
• 0.5 teaspoons vanilla
• 1 cup all-purpose flour
• 0.5 teaspoons baking soda
• 0.5 teaspoons baking powder
• 0.25 teaspoons salt
• 0.5 cups plus 1 tablespoon cocoa (or just a heaping half cup)
• 0.5 cups boiling water
  

Melt the butter, then mix in the brown sugar, eggs, yogurt, and vanilla.  Add the flour, baking soda, baking powder, salt, and cocoa (mixing the dry ingredients first if you want, but I'm usually lazy and just add them straight to the wet ingredients, making sure to disperse the teaspoons of leavening and salt evenly across the batter surface).  Mix in the boiling water and pour the batter on top of the frosting in the pan.

Bake until a knife comes out clean from the cake layer.  I haven't actually tried to flip the cake out, and instead generally just scoop individual slices out of the pan and serve them jam-side-up, but it might work to decant the cake for party presentation.  Be sure to serve warm so the frosting is flowable.  This recipe serves 8 chocoholics or 16 people with self-restraint.