This was passed down to me from my mother. This was my favorite cake growing up (and still is). Everyone would ask her to make this for our family gatherings. Now that she is no longer with us, I am proud to be able to still make this cake in honor of her.
Preheat oven to 350 degrees. Mix all ingredients, except marshmallows, in mixing bowl.
Pour into 9x13-inch pan. Place into oven and bake for 35-40 minutes.
While cake is baking, prepare the icing. In a mixing bowl add cocoa, powdered sugar, margarine and evaporated milk. Mix with electric hand mixer. Set aside.
Remove cake from oven and while the cake is still hot pour marshmallows over cake. Then spread icing on top. Allow cake to sit at room temperature for about 45 minutes before serving to allow icing to set up.