A PERFECT BUFFET CAKE WITH FILLING AND GLAZE

I have had this recipe for so many years I have no idea where I got it. The picture is the one that I got with it.
1 1/4 cups all-purpose flour
1 cup + 1/2 cup granulated sugar
1/2 cup unsweetened baking cocoa
3/4 tsp baking soda
1/2 tsp salt
1/2 cup canola oil
2 eggs, separated
1 cup buttermilk
1 tsp vanilla extract
Chocolate Filling (recipe below)
Chocolate Glaze (recipe below)
Whipped cream, for garnish
Maraschino cherries, for garnish

Preheat oven to 350 degrees.
Line a 15 x 10-inch baking pan with foil; grease and lightly flour the foil.  Set prepared pan aside.

In a large mixer bowl mix the flour, 1 cup of the granulated sugar, baking cocoa, baking soda, and salt.  Add the canola oil, egg yolks, buttermilk, and vanilla extract; beat mixture until smooth.

In another mixer bowl, beat the egg whites until foamy.  Gradually add the remaining half cup of sugar and beat until sugar is dissolved and whites are stiff.  Fold the whites into chocolate batter.  Pour the batter into the prepared pan.

Bake at 350 degrees for 25 to 30 minutes or until the cake springs back when lightly touched in the center.  Cool in the pan for three minutes.  Invert the cake onto a large cooling rack and carefully remove the foil.  Allow cake to cool completely.

While cake cools, make the Chocolate Filling.

Cut the cooled cake in half crosswise making two equal layers.  Place 1 layer on the serving platter.  Spread the chocolate filling over the cake layer.  Top with the remaining layer.  Refrigerate to chill while you make the Chocolate Glaze.

Spoon the glaze over the top of the cake and chill for about 2 hours to set the glaze.

To serve, garnish with swirls of whipped cream.  Top each whipped cream swirl with a maraschino cherry.

Yield: 12 servings.

CHOCOLATE FILLING:
1/2 cup unsalted butter, softened
2/3 cup granulated sugar
1 egg
1/3 cup unsweetened baking cocoa
1 tsp vanilla extract (use rum extract, if desired)
1/2 cup whipping cream

In a mixer bowl combine the softened butter, granulated sugar, egg, cocoa, and extract; beat until smooth.

In a separate bowl beat the whipping cream to stiff peaks.  Gently fold egg whites into the chocolate mixture.

CHOCOLATE GLAZE:
2 tbsp butter
3 tbsp unsweetened baking cocoa
3 tbsp water
1/2 tsp vanilla extract
1 1/4 to 1 3/4 cups powdered sugar

Melt the butter in a small saucepan over low heat.  Stir in the cocoa and water.  Cook mixture until thickened while stirring constantly; do NOT boil.  Remove from the heat.

Add the vanilla extract and the powdered sugar (start with 1 1/4 cups and increase if too thin), beating until smooth.