You need an iron skillet to make this. I'm sure you could use a round cake pan also.
1 1/2 cup plain flour (I use 100% white whole wheat)
1 c sugar (I use 3/4 cup and add some applesauce)
3 tablespoons cocoa powder
1 teaspoon baking soda
Mix the above ingredients together in an ungreased iron skillet. Make 3 holes with the back of a spoon in the dry mix.
Place one of the next three ingredients in each hole.
6 tablespoons oil (I use coconut oil)
1 Tablespoon vinegar
1 teaspoon vanilla
DO NOT MIX !
Pour 1 cup of cold water over it all and then stir with a spoon until smooth.
Bake at 350 degrees for about 25 minutes, check to see if it is done by inserting a knife in the middle of the cake. If the knife comes out clean it is done, if not let it bake a few more minutes and check again.
Let cake completely cool in the skillet.
1 1/2 cup confectioners sugar
2 tablespoons cocoa powder
3 tablespoons softened butter (not melted)
2 tablespoons milk
Stir together until it is smooth. Spread on the cake when it is completely cooled.