Step 1

Preheat oven to 350F. Butter and flour three 6 inch round pans. Whisk together the flour, baking powder, corn starch, and salt then set aside.

Step 2

Cream butter and sugar in a stand mixer using a paddle attachment, or a large bowl if using an electric hand mixer.

Step 3

Add the oil and vanilla, mix to combine then scrape the bowl down. Add the eggs one at a time mixing until incorporated before adding the next. Scrape the bowl down once more and mix again.

Step 4

Add flour mixture and buttermilk to the butter in alternating batches while mixing on low.

Step 5

Bake at 350F for about 30 minutes or until the centers are set and springy.

Step 6

Allow to layers cool in pans for a few minutes then invert into a wire rack to cool completely.

Step 7

Melt 1/4 cup of the butter in a microwave. Mix in the cocoa power and set aside.

Step 8

Melt 1/3 cup of semisweet chocolate with 1/4 cup milk then mix together and set aside. You can use 1/2 cup of chocolate for an extra-rich frosting if desired.

Step 9

Beat one cup of room temperature butter in a stand mixer using a paddle attachment, or a large bowl if using an electric hand mixer.

Step 10

Pour in the melted butter cocoa mixture, mix to combine then scrape the bowl down and mix again. Add the powdered sugar and mix on low. Pour in the melted and cooled chocolate ganache then drizzle in about 1/4 cup of milk. Scrape the bowl down and mix until smooth. Your frosting should be silky, soft and luscious.

Step 11

Pipe or spread the buttercream onto the first layer, add the next layer on top and repeat until the cake Is built. Cover the cake with buttercream then use a spatula to swirl the buttercream around for a rustic effect.