Preheat the oven to 325°F (160°C). Prepare two 9-inch (22 cm) cake pans with non-stick baking spray and parchment circles.

In a mixing bowl, whisk the flour, baking soda, baking powder, salt, and mini chocolate chips.

In another heatproof bowl, combine the unsweetened chocolate, cocoa powder, and optional espresso powder. Pour the hot water over the mixture and let it bloom for at least 5 minutes, then stir it into a glossy paste.

In a stand mixer or large bowl, beat the butter, brown sugar, and granulated sugar until fluffy. Add the eggs one at a time, scraping down the sides after each addition. Mix in the chocolate mixture and vanilla.

With the mixer on low, add the dry mixture in three additions, alternating with the sour cream and buttermilk. Begin and end with the flour mixture. Mix only until combined, because overmixing can make the cake tough.

Divide the batter evenly between the prepared pans. Bake until the cakes bounce back when lightly touched and a toothpick inserted in the center shows moist crumbs, about 28 to 35 minutes. Cool the cakes in the pans for 15 minutes, then turn them out onto a wire rack to cool completely.

While the cakes bake, make the cherry compote. Stir the cornstarch and water together in a small bowl to create a slurry. Place the cherries, 1/2 cup plus 2 tablespoons sugar, orange zest, and orange juice in a medium saucepan. Cook over medium heat until the sugar dissolves and the cherries release their juices. Re-stir the slurry, slowly add it while stirring, and continue cooking until the mixture thickens. Stir in the vanilla, transfer to a bowl, and chill.

For the optional syrup, combine the simple syrup, 2 tablespoons of liquid from the chilled cherry compote, and Kirsch or cherry liqueur. Set aside.

Right before assembly, make the mascarpone frosting. Combine the mascarpone, powdered sugar, heavy cream, and orange zest. Whip on low until incorporated, then increase to high and beat until firm peaks form. Stop before the mixture becomes grainy.

For the ganache, combine the chocolate chips and heavy cream in a microwave-safe bowl. Microwave for 1 minute, stir, then microwave in 15 to 30 second intervals as needed. Stir until thick and shiny, then let it cool slightly until spreadable.

Place one cake layer on a cake plate and brush or spoon over the optional syrup. Pour half the ganache over the layer and spread it to the edge. Cover with half of the chilled cherry compote, then pipe small swirls of mascarpone frosting over the compote.

Add the second cake layer and repeat the syrup, ganache, compote, and mascarpone frosting layers. Garnish with fresh cherries. Serve any extra compote, ganache, or frosting alongside the slices.

For the cleanest slices, refrigerate the assembled cake for about 30 minutes before cutting. Bring slices back to room temperature before serving so the chocolate cake texture stays soft and tender.