Yellow Sheet Cake with Chocolate Frosting

Here is a juicy, buttery dessert that will turn any event into a holiday. Our staff liked it and received top marks for its taste. Fresh edible flowers, such as mummies, easily and beautifully decorate the cake; most people clean the flowers before eating. If you're offering a pie at an informal meeting, serve it straight from the pan.
Preheat the oven to 350 degrees.To make the pie, brush the bottom of a 13-inch x 9-inch baking dish with cooking spray (do not grease the sides of the pan); cover the bottom of the pan with waxed paper. Brush waxed paper with cooking spray; sprinkle with 1 tablespoon flour. Set aside.Combine 1/2 cup butter and sour cream in a large bowl, stirring with a whisk until smooth. Add the granulated sugar and 2 teaspoons of vanilla. Beat with a mixer on medium speed for 3 minutes or until smooth. Add egg substitute; beat for 2 minutes or until smooth.Lightly pour 2 cups flour into dry measuring cups; smooth with a knife. Combine 2 cups flour, baking soda, and 1/2 teaspoon salt, mixing well with a whisk. Add the flour mixture and buttermilk alternately to the sugar mixture, starting and ending with the flour mixture; stir after each addition. Pour the batter into the prepared pan. Tap the baking tray sharply on the countertop once to remove any air bubbles. Bake at 350 ° C for 30 minutes or until a wooden stick inserted in the middle comes out clean. Cool in the pan for 10 minutes on a wire rack; remove from the pan. Carefully remove the wax paper; cool completely on a wire rack.To make the frosting, put the cream cheese, 1/4 cup butter, and 1 teaspoon vanilla in a large bowl; beat with a mixer on high speed until fluffy. Add the cocoa, milk, and 1/8 teaspoon salt; beat on low speed until smooth. Gradually add 1 1/2 cups powdered sugar; beat on low speed until creamy. Gradually add the remaining 1 1/2 cups powdered sugar. Place the cake on a serving platter. Spread the icing on the top and sides of the cake. Keep the cake loosely covered in the refrigerator.