01 -
Preheat oven to 350°F. Spray a 9×13-inch baking pan with baking spray. Place chocolate chips in a bowl. Heat milk to 180-190°F and pour over chocolate chips. Let sit 5 minutes, then whisk until smooth. Stir in sour cream until fully combined. Set aside.
02 -
In a medium bowl, whisk together cake flour, cocoa powder, baking soda, and salt. Set aside.
03 -
In a large bowl, beat brown sugar and vegetable oil until combined. Add vanilla extract and eggs one at a time, mixing until incorporated.
04 -
Add half of the dry ingredients to the wet mixture and stir until combined. Add half of the chocolate and sour cream mixture and combine. Repeat with remaining dry and wet ingredients until batter is smooth.
05 -
Pour batter into prepared pan. Bake on the middle oven rack for 30 to 35 minutes or until a toothpick inserted in the center comes out clean. Cool completely.
06 -
Whisk milk and flour in a small saucepan. Cook over medium heat, stirring constantly, until thickened into a paste. Remove from heat and cool to room temperature.
07 -
In a large bowl, beat butter and shortening until combined. Gradually add powdered sugar and mix well. Stir in cooled milk-flour paste and vanilla extract. Whip on medium-high speed for 3 minutes until fluffy and smooth.
08 -
Spread the cream filling evenly over the cooled cake. Refrigerate while preparing ganache.
09 -
Warm heavy cream to 180-190°F and pour over chocolate chips in a bowl. Let sit 5 minutes, then whisk until smooth. Cool slightly for 10 minutes.
10 -
Pour ganache over cream-covered cake, smoothing the surface. Refrigerate uncovered for 45 minutes to set. Slice and serve.