113.25 or 15.25 ozbox chocolate cake mix plus eggsoil and water as directed on the box
Frosting:
6tablespoonsunsalted or salted buttersoftened
2cupsconfectioners’ sugar (you can use more if needed)
½cupnatural style cocoa powder, sift out any lumps
⅛teaspoonsalt (not necessary if using salted butter)
¾teaspoonvanilla extract
⅓cupwhole milk or half & half or a little of eachplus more as needed
Instructions
Preheat oven to 350 degrees F. Grease and flour a 9x13 inch baking pan.
Make the white filling first. In a mixing bowl, beat together the cream cheese, butter, sugar, cornstarch, milk and vanilla until creamy and smooth. Add the egg and beat just until mixed. Set aside.
Prepare the cake mix using the directions on the side of the cake mix box. Pour a little over half of the cake mix into the pan, spoon the white mixture as evenly as possible over the top, then pour the rest of the cake batter over the white. Bake on center rack for 30 to 33 minutes (or time given on the box).
Let cool, then cover with chocolate frosting.
One Bowl Chocolate Frosting
Make the chocolate frosting. In a large mixing bowl, mix the softened butter, sugar, cocoa, salt, vanilla and 2 tablespoons of the milk as well as you can, then beat with an electric mixer until pasty and thick. Continue adding milk until consistency is smooth and spreadable. Spread over the cake and chill.