Firstly, in a small heat safe bowl, add cocoa powder and boiling water to bloom the cocoa powder. Stir to combine, and let it sit for 5 minutes or so to cool while you mix up your other ingredients.
Mill the flour, I use a soft white wheat.
Add Potato Starch, baking soda, baking powder, and salt into your flour. Wisk these dry ingredients together, then set aside while you mix your wet ingredients.
In a separate mixing bowl, add melted butter, sugar, eggs, vanilla, vinegar, and buttermilk. Beat together until wet ingredients are combined, and fluffy.
Add the cocoa mixture, and beat to combine.
Then, add the dry ingredients to the wet ingredients. Stir these together to combine. You want it smooth and incorporated, but not over mixed. Do this part by hand, not with a mixer.
Let your batter sit for about 15 minutes while the oven preheats and you prepare your baking pans.
Preheat oven to 325* F
Prepare your cake pans. (I use softened butter, and heavily butter my two 8 inch round cake pans. Then, I cut a piece of parchment paper in a circle to line to bottom of the pan. Then, coat that with softened butter as well to prevent the cake from sticking.)
Evenly distribute batter into both prepared round cake pans. I used Two- 8 inch cake pans. (*Alternate Pan size baking instructions below.)
Bake for about 33-38 minutes, or until an inserted toothpick comes out clean. Keep an eye on it, you don't want to overbake or it will be dry. I look for the edge of the cake to start to barely pull away from the side of the cake pan.
Allow cakes to cool in the pan for about 15 to 20 minutes.
Then, turn each cake out onto a wire rack to cool completely before frosting. (I highly recommend putting them in the freezer before frosting, so that they are easier to frost, and it will help the cakes to not fall apart as easily.
Make The Frosting While the cakes are cooling.