Preheat your oven to 350°F (175°C). Grease two 8-inch or 9-inch round cake pans and line the bottoms with parchment paper.
In a large bowl, cream the butter and sugar together until light and fluffy. Add the eggs, one at a time, mixing well after each addition.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk, beginning and ending with the dry ingredients. Stir in the vanilla extract.
Divide the batter evenly between the prepared pans. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
For the frosting, beat the butter until smooth. Gradually add the powdered sugar, cocoa powder, and vanilla. Add milk, one tablespoon at a time, until the frosting reaches your desired consistency.
Frost the cooled cake layers, then enjoy!
Alternate Instructions
Preheat oven to 350°F and prepare cake pans with grease and parchment paper.
Cream butter and sugar until fluffy, then mix in eggs one at a time.
Combine dry ingredients (flour, cocoa powder, baking soda, salt) in a separate bowl.
Alternate adding dry ingredients and buttermilk to the wet mixture. Stir in vanilla.
Pour batter into pans, bake for 25-30 minutes, and cool completely before frosting.
Whip up frosting by beating butter, powdered sugar, cocoa, and vanilla. Add milk to adjust consistency, then frost and serve.