This hot fudge cake recipe really satisfies my chocolate craving, too.  
It is very sweet however.

Hot fudge cake

1 cup flour
3/4 c sugar
6 tbls baking cocoa, divided
1/4 tsp salt
1/2 c skim milk
1 tsp vanilla
1 c packed brown sugar
1 3/4 c hot water

In a medium bowl, combine flour, sugar, 2 Tbls cocoa, baking powder and 
salt.  Stir in the milk and vanilla until smooth.  Spread in aan 
ungreased 9-in square baking pan.  Combine brown sugar and remaining 
cocoa; sprinkle over batter.  Pour hot water over all; do not stir.  Bake 
at 350 degrees for 35-40 minutes.  Serve warm.  I like to serve it with 
frozen non-fat vanilla yogurt.  Yield: 9 servings.