Preheat oven to 350. Prepare pans by cutting out parchment to line bottom of pan. Lightly grease pan(s) (so parchment will lay flat), then place parchment in bottom of pan. Lightly grease parchment and then dust with flour. For cupcakes- place cupcake liners in pan.
Using a fine strainer over your mixing bowl sift: cocoa powder, flour, sugar, baking soda, baking powder, and salt.
Add egg, egg yolk, coffee (or water), buttermilk, oil, and vanilla
Mix on low speed in stand mixer or with hand mixer until smooth- just a few minutes.
Pour batter evenly into prepared pans. Or fill cupcake liners 2/3 full- an ice cream scoop works great here.
Bake in preheated oven until toothpick inserted in center comes out clean- be careful not to over bake!
Approx: 30-35 min for round pans, 16-20 min for cupcakes, 40-45 min for 9x13 pan (These times are approximates as every oven can be very different- so just check towards end of baking times and adjust times as necessary!)
Remove from oven and place pans on cooling racks for 15min then run a knife around edges, remove from pans and allow to cool top side up on cooling racks. After completely cool, frost and enjoy!!