Step 1

Stir 1/4 cup of the sugar together with the cornstarch in a small mixing bowl and set aside.

Step 2

Crack the eggs into a medium heat-proof bowl. Whisk the eggs together and and set the bowl next to the stove.

Step 3

Combine the milk and remaining 1/4 cup of sugar in a small saucepan set over medium heat and bring to a simmer, stirring occasionally.

Step 4

Once the milk has come to a simmer, whisk the sugar-cornstarch mixture into the eggs until smooth.

Step 5

Whisking the eggs constantly, add a scant 1/4 cup of the hot milk to the eggs. Still whisking constantly, pour the remaining milk into the eggs in a slow stream.

Step 6

Return the mixture to the saucepan and set pan over medium-low heat. Cook, stirring constantly with a rubber spatula, until the mixture thickens a bit—it will start to get lumpy.

Step 7

Turn the heat to low and switch to stirring with a whisk. Whisk vigorously until the mixture is very thick and smooth—if you don’t get your pudding completely smooth, you’ll have lumps in your frosting.

Step 8

Remove from the heat and stir in the 2 tablespoons of butter.

Step 9

Scrape the pudding into a shallow mixing bowl and press plastic wrap directly on the top of the pudding. Chill in the fridge for 90 minutes to 2 hours (or until thoroughly chilled).  You'll finish the frosting later.  While the pudding is chilling, make the cake.

Step 10

Preheat the oven to 350 degrees. Spray a 13- by 9-inch baking pan with cooking spray and set aside.

Step 11

Whisk the flour, baking powder, baking soda and salt together in a small mixing bowl and set aside.

Step 12

Beat the butter in a large mixing bowl with an electric mixer set to medium until very smooth. Beat in the sugar and vanilla until well combined (mixture will be crumbly). Add the egg whites one at a time, beating well after each addition.

Step 13

With mixer on low, beat in half of the flour mixture followed by half of the buttermilk and beat to combine. Add the remaining flour mixture, then the remaining buttermilk and beat until just incorporated.

Step 14

Spread three-quarters of the batter into the prepared pan. Sift the cocoa powder over the remaining batter and add the milk; stir until fully combined.

Step 15

Dollop the chocolate batter over the vanilla batter and carefully spread into an even layer with an offset spatula (don’t swirl them together, just spread the chocolate batter over the vanilla). Sprinkle the drained cherries over the cake batter.

Step 16

Bake 35 to 40 minutes, until a cake tester inserted into the center of the cake comes out clean.

Step 17

Remove cake from the oven and cool completely on a wire rack before adding the frosting.

Step 18

Once the pudding and the cake are both cooled, finish the buttercream. Remove the chilled pudding from the fridge and allow it to come to room temperature.

Step 19

Transfer the room temp pudding to the bowl of a stand mixer fitted with the whisk attachment and beat on medium for several minutes, until it’s very light and creamy.

Step 20

With mixer still on medium speed, add the butter half a tablespoon at a time, stopping mixer to scrape with a rubber spatula every so often.

Step 21

Once the butter is fully incorporated, add the powdered sugar, vanilla, and salt, and beat until smooth. Spread over the fully cooled cake. Refrigerate for 1 hour to set the buttercream before adding the chocolate topping.

Step 22

Place the chocolate in a small heat-proof bowl. Heat the cream in a medium saucepan set over medium heat until it just begins to steam. Pour over the chocolate and allow to sit for 3 minutes.

Step 23

Add the corn syrup, then whisk the chocolate and heavy cream together until the chocolate is melted and mixture is smooth. Allow to cool for 10 minutes.

Step 24

Remove cake from the fridge and spread the chocolate into an even layer over the buttercream. Refrigerate to set the ganache, then serve.