1.In a medium bowl, whisk together the flour,
baking soda, baking powder, and salt. Set aside.
2. In a standing mixer fitted with the paddle
attachment, beat the butter at medium speed
until smooth, about 2 minutes. Increase the
speed to medium-high and slowly add the sugar.
Continue beating until light and smooth, about 4
minutes.
3. Turn the mixer off and scrape down the
sides of the bowl with a rubber spatula.
4. Add the cocoa powder and vanilla and
beat at medium speed for 1 minute more.
5. With the mixer running at medium-low
speed, add the eggs, one at a time, beating for
1 minute between each addition. Scrape down the
sides of the bowl.
6. Combine the water and milk in a saucepan
and bring just to a boil. Remove from the heat.
7. With the mixer at low speed, add the flour
mixture, about a 1/4 cup at a time. Carefully
pour the hot liquid into the batter. Remove the
bowl from the mixer and, using a large rubber
spatula, finish combining the batter until
smooth.
8. Divide the batter evenly between the
prepared pans. Lightly drop each pan onto the
counter to settle the batter.
9. Set the pans on the middle rack in the
oven. Bake until the cakes begin to pull away
from the sides of the pans and the center
springs back when touched lightly, about 30 to
35 minutes.