Prepare the Chocolate Sponge
Preheat and prep: Position rack in center of oven and preheat to 325°F (160°C). Grease a 9×13-inch baking pan and line with parchment paper, leaving overhang on long sides for easy removal.

Combine dry ingredients: In a large bowl, whisk together flour, cocoa powder, baking soda, baking powder, salt, and sugar until no lumps remain.

Mix wet ingredients: In a separate bowl, whisk together eggs, vegetable oil, buttermilk, and vanilla until smooth.

Combine: Pour wet ingredients into dry ingredients and whisk until just combined—some small lumps are fine. With mixer on low speed, carefully stream in hot coffee, mixing until batter is smooth and pourable. The batter will be quite thin; this is correct and creates Ruby's signature tender crumb.

Bake: Pour batter into prepared pan. Bake 30-35 minutes until toothpick inserted in center comes out with just a few moist crumbs. Top should spring back when gently pressed.

Cool completely: Allow cake to cool in pan for 15 minutes, then use parchment overhang to lift onto wire rack. Cool completely before proceeding—essential to prevent ganache from melting.

Prepare the Boozy Cherry Layer
Macerate the cherries: Drain Morello cherries, reserving ½ cup syrup. In a bowl, toss cherries with kirsch. Set aside for at least 20 minutes, stirring occasionally.

Make the cherry compote: In a small saucepan, whisk together ¼ cup reserved cherry syrup with sugar and cornstarch until smooth. Cook over medium heat, stirring constantly, until thickened and glossy, about 2-3 minutes. Remove from heat.

Combine: Gently fold macerated cherries with their liquid into thickened syrup. Set aside to cool to room temperature.

Make the Dark Chocolate Ganache
Heat the cream: In a small saucepan, heat cream over medium heat until it just begins to simmer—small bubbles will form around edges.

Create the ganache: Place chopped chocolate in a heatproof bowl. Pour hot cream over chocolate and let stand 2 minutes without stirring. Beginning in center and working outward in small circles, whisk gently until completely smooth and glossy.

Finish the ganache: Whisk in butter and kirsch until incorporated. Let cool slightly until spreadable but still pourable, about 10-15 minutes at room temperature.

Make the White Chocolate Drizzle
Melt the white chocolate: Place white chocolate in a heatproof bowl. Heat cream until just simmering, pour over chocolate, and let stand 1 minute. Stir gently until smooth. Transfer to piping bag fitted with small round tip.

Assemble the Traybake
Soak the sponge: Combine reserved ¼ cup cherry syrup with 2 tablespoons kirsch. Using pastry brush, generously brush mixture over top of cooled cake, allowing it to soak in.

Add the cherry layer: Spoon cherry compote evenly over soaked sponge, spreading gently with offset spatula. Reserve 16-20 whole cherries for garnish.

Apply the ganache: Pour slightly cooled ganache over cherry layer. Use offset spatula to spread into even layer, working quickly before it sets. Allow to set slightly, about 5-10 minutes.

Pipe the white chocolate: Working quickly, pipe white chocolate in parallel lines across width of cake. Immediately drag toothpick or skewer lengthwise through lines in alternating directions to create elegant feathered pattern.

Garnish: Arrange reserved cherries in decorative pattern and scatter chocolate shavings around them.

Chill: Refrigerate traybake for at least 2 hours, or preferably overnight. As Ruby noted, proper chilling is essential—otherwise the tender sponge and rich ganache create a sloppy mess.

To Serve
Use sharp knife dipped in hot water and wiped clean between cuts to slice into portions. Allow slices to come to cool room temperature for 10-15 minutes before serving for best texture and flavor.