Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 9 inch, round, cake pans; cover bottoms with waxed paper.
In a large bowl, combine flour, 2 cups sugar, cocoa, baking powder, baking soda, and salt. Add eggs, milk, oil, and 1 tablespoon vanilla; beat until well blended. Pour batter into prepared pans.
Bake for 35 minutes, or until wooden toothpick inserted in centers comes out clean. Cool layers in pans on wire racks 10 minutes. Loosen edges, and remove to racks to cool completely.
Drain cherries, reserving 1/2 cup juice. Combine reserved juice, cherries, 1 cup sugar and cornstarch in a 2 quart saucepan. Cook over low heat until thickened, stirring constantly. Stir in 1 teaspoon vanilla. Cool before using.
Combine whipping cream and confectioner's sugar in a chilled medium bowl. Beat with an electric mixer at high speed until stiff peaks form.
With long serrated knife, split each cake layer horizontally in half. Tear one split layer into crumbs; set aside. Reserve 1 1/2 cups Frosting for decorating cake; set aside. Gently brush loose crumbs off top and side of each cake layer with pasty brush or hands. To assemble, place one cake layer on cake plate. Spread with 1 cup frosting; top with 3/4 cup cherry topping. Top with second cake layer; repeat layers of frosting and cherry topping. Top with third cake layer. Frost side of cake. Pat reserved crumbs onto frosting on side of cake. Spoon reserved frosting into pastry bag fitted with star decorator tip. Pipe around top and bottom edges of cake. Spoon remaining cherry topping onto top of cake.
Why Halving Layers Requires Precision
When downsizing a formula built for two nine-inch pans, weight measurements prevent dry sponge failures. Flour behaves unpredictably when volume cups are halved, so converting dry components to grams ensures the crumb retains its structural integrity. Baking temperatures must remain constant at 350 degrees Fahrenheit regardless of batch size, though smaller pans require checking with a wooden toothpick five minutes early to prevent over-baking.
Balancing Fruit and Fat Ratios
Cornstarch thickens fruit fillings through gelatinization, requiring a sustained simmer at low heat until the liquid turns translucent. Excessive liquid prevents the heavy cream frosting from adhering properly to the sponge layers. Chilling the mixing bowl before whipping the cream traps air bubbles efficiently, yielding the stiff peaks necessary for piping decorative borders through a star tip.
Managing Second-Day Textures
Refrigeration causes starches in the baked chocolate layers to retrograde, hardening the crumb structure if left uncovered. Storing leftover slices in an airtight container for up to forty-eight hours maintains moisture balance between the dairy and the cherry compote. Allowing chilled portions to sit at room temperature for fifteen minutes softens the butterfat in the whipped cream frosting.