- Place a strainer over a large mixing bowl. Measure in the flour, baking powder, baking soda, salt, cocoa, and sugar. Sift/shake the dry ingredients through the strainer into a mixing bowl, to eliminate any lumps.
- Add the butter and mix at low speed for 1 minute. With the mixer running, add the oil and continue mixing until the mixture looks like sand.
- Combine the vanilla with the milk and coffee or water, and add all at once. Mix for 1 minute at low speed, stop and scrape the sides and bottom of the bowl, then mix for 30 seconds.
- Add the eggs one at a time, beating well at medium-high speed between additions. The batter will be thin.
- Pour the batter into the prepared pan of your choice (one 9" x 13" pan, two 9" round pans, or three 8" round pans). Bake in a preheated 350°F oven for 34 minutes for a 9" x 13" pan; 28 to 30 minutes for 9" layers; or 24 to 26 minutes for 8" layers. The cake is done when a toothpick inserted in the center comes out clean. Remove from the oven and cool on a rack before frosting.