Grease and lightly flour a 9X13 baking pan. Preheat oven to 350 degrees.
You can use a standing mixer with this recipe or combine by hand. Combine all dry ingredients into a bowl and blend.
Combine all wet ingredients in a seperate bowl, if mixing by hand.
Make a well in the dry ingredients and pour wet ingredients into the well. Mix until well blended.
Pour into prepared baking dish and bake for 35 minutes.
Once cake is done, begin making the frosting.
In a medium sauce pan, mix sugar, cornstarch; add chocolate and salt. Add boiling water, slowly stiring constantly. Begin cooking on medium high setting. Add butter and vanilla. Cook until the mixture thickens into a pudding consistency. Pour over warm cake.