Combine the sugar, flours, baking soda, and salt in the bowl of a stand mixer fitted with the paddle attachment. Whisk the oil, sour cream, eggs, and egg yolks in a large pourable vessel. Add the oil mixture to the cocoa and water mixture and slowly whisk to combine. With the mixer on low speed, add the liquid mixture to the dry mixture over 30 seconds. Continue to beat on low speed for another 30 seconds. Stop and scrape down the sides of the bowl. Continue to beat on low speed until the batter is smooth, 10 to 15 seconds. Pour the batter into the prepared pan and bake until the cake springs back when pressed and reaches an internal temperature of 205 degrees F, 30 to 35 minutes.