Combine all ingredients in a large mixing bowl and mix by hand with a wooden spoon until well blended and smooth. Spread into a greased 9x13 cake pan.
Bake at 350 for 45 minutes.
Stir together butter, cream, and brown sugar in a sauce pot. Place over medium heat and stir constantly until butter is melted and mixture is well blended. Turn heat up to medium high and stir constantly until it comes to a rolling boil. Once boiling, cook for 2 minutes and then remove from heat. Stir in confectioners sugar and vanilla until smooth. Work quickly and use a wire whisk or electric mixer if you prefer. You can add up to 1/2 cup more confectioner's sugar if needed to thicken. Ice cooled cake as soon as possible.
If you were born after 1950, don't try to ice a layer cake with a boiled icing. Stick with 9x13 sheet cakes. Trust me :)