• Preheat oven to 375.
• In a medium bowl, sift flour, sugar, salt, and baking soda together.
  2 cups plain flour, 2 cups granulated sugar, 1/2 tsp salt, 1 tsp baking soda
• Bring butter, oil, cocoa, and one cup of water to a boil, stirring constantly.
  1 stick unsalted butter, 1/2 cup vegetable oil, 4 tbsp unsweetened cocoa powder, 1 cup cold water
• Once it boils, remove the pot from the heat and combine the cocoa mixture with the flour mixture in a mixing bowl.
• Add eggs, one teaspoon of cold water, and buttermilk, and mix well.
  2 eggs, beaten, 1/2 cup buttermilk, 1 cup cold water
• Pour into a greased and floured 9x13 baking dish and bake for 25-30 minutes.
• Top with marshmallows while warm and make icing while the cake is baking.
  10 oz marshmallows

Chocolate Icing

• Combine butter, cocoa, and milk in a saucepot and bring to a boil. 
  1 stick unsalted butter, 3 tbsp unsweetened cocoa powder, 6 tbsp whole milk
• Remove from heat and mix in the sugar and vanilla.
  16 oz confectioner's sugar (or powdered sugar), 1 tsp vanilla extract
• Pour the icing over the hot cake as soon as it comes out of the oven.