What you discribe sounds like any cake that you would pour a syrup over after it is baked like "Better Then Sex cake". It is very simple to make. Just make chocolate cake from a mix following direction for a 9"X13". Poke holes all over the hot cake with the round handle of a wooden spoon. Then pour a can of sweetened condensed milk and a jar of carmel ice cream topping (I like Mrs. Richarson's 17-18 oz) Let cool. Then frost with a 8 oz. tube of Cool Whip. Store in the refrigerator. You can sprinkle crushed "Heath bar" or brickle chip on top if you like.
Note: I suppose you could use chocolate sweetened condensed milk and hot fudge or chocolate topping but the would be very,very intense chocolate flavor.

Another moist cake is:

CRAZY CAKE/MARSHMALLOW FROSTING

Mix with fork in 9 x 13 pan(ungreased)...
3 c. flour
1/3 c. cocoa
2 c. sugar
dash salt
2 t. soda
Stir together in small bowl...........
3/4 c. oil
2 T. vinegar
2 c. water
2 t. vanilla
Pour wet mixture into three wells in dry mixture. Stir with
a fork until well blended. Bake at 350 degrees for 45 minutes.

Marshmallow Frosting:

PLace in top of double boiler........
2 egg whites
1/2 c. white corn syrup
1/2 c. sugar
1/8 t. salt
Beat until partially mixed.Place over rapidly boiling and beating
constantly until frosting stands in peaks, 3 to 4 minutes.

Add and continue beating until melted ..............
3/4 c. fresh mini marshmallows
Remove from heat and continue beating about 1 minute.
Add...............
1 t. vanilla
Beat well and frost.