Step 1

Mix together flour, sugar and salt in a small mixing bowl.

Step 2

In a small sauce pan combine butter, cocoa and water. Stir until butter melts and mixture comes to a boil.

Step 3

Pour mixture over dry ingredients and stir to combine.

Step 4

Add in egg yolk, buttermilk, baking soda and vanilla. Stir to combine.

Step 5

Pour mixture into a greased 9 x 7 inch baking pan.

Step 6

Bake at 350 degrees for 15 minutes or until toothpick comes out clean.

Step 7

As soon as cake comes out of oven mix up frosting.

Step 8

In a small sauce pan combine butter ,milk, cocoa powder, and powdered sugar.

Step 9

Stir until butter melts and ingredients are combined. Frosting will be thin. Do not allow it to boil.

Step 10

Add in vanilla.

Step 11

Pour hot frosting over hot cake out of the oven.

Step 12

Spread to cover cake.