01 -
Preheat oven to 350°F. Spray a 9x13 inch baking dish with baking spray. Heat 3/4 cup milk until between 180-190°F. Pour hot milk over 1 cup chocolate chips in a bowl and let sit 5 minutes. Whisk until smooth, then stir in sour cream until combined. Set aside.
02 -
In a medium bowl, whisk together cake flour, all-purpose flour, cocoa powder, baking soda, and salt. Set aside.
03 -
In a large bowl, beat brown sugar and vegetable oil with an electric mixer until combined. Add vanilla and eggs one at a time, mixing until fully incorporated.
04 -
Add half of the dry ingredients to the wet mixture, mixing to combine. Add half of the chocolate/sour cream mixture, mix well. Repeat with remaining dry and wet ingredients until fully combined.
05 -
Pour batter into prepared dish. Bake on middle oven rack for 30-35 minutes or until a toothpick comes out clean. Cool completely.
06 -
Whisk milk and flour in a small saucepan. Cook over medium heat, stirring constantly, until mixture thickens to a paste. Cool to room temperature.
07 -
Beat butter and shortening in a large bowl until combined. Gradually add powdered sugar until thick. Stir in cooled milk/flour paste and vanilla extract. Whip on medium-high speed for 3 minutes until light and fluffy.
08 -
Spread filling evenly over cooled cake. Refrigerate while preparing ganache.
09 -
Heat heavy cream to 180-190°F. Pour over 1 cup chocolate chips and let sit 5 minutes. Whisk until smooth, then let cool 10 minutes.
10 -
Pour ganache over filled cake. Refrigerate uncovered for 45 minutes until set. Slice and serve.