Preheat oven to 350°F (175°C). Grease and flour your cake pans.
Whisk dry ingredients: In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt.
Cream butter and sugar: In another bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla extract.
Combine wet and dry ingredients: Add dry ingredients to wet ingredients in batches, alternating with buttermilk, until just combined. Do not overmix.
Divide batter evenly between prepared pans and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. Cool cakes in pans for 10 minutes, then transfer to wire racks to cool completely.
Make cherry filling: While cakes cool, in a small saucepan, combine drained cherries, cherry brandy (if using), cornstarch, and water. Bring to a simmer over medium heat, stirring constantly, until thickened. Let cool slightly.
Whip cream: In a cold bowl, using a hand mixer or stand mixer with the whisk attachment, whip heavy cream, powdered sugar, and vanilla extract until stiff peaks form.
Assemble cake: Once cakes are cooled, level off any uneven tops. Place one cake layer on a serving platter. Spread with cooled cherry filling, then top with a generous layer of whipped cream. Place the second cake layer on top and frost the entire cake with remaining whipped cream.
Decorate: Drizzle melted chocolate over the top of the cake, creating swirls and drips. Garnish with fresh cherries, if desired.
Chill for at least 2 hours before serving to allow the flavors to meld and the cake to set.