Preheat oven to 350F. Grease and flour two 9-inch round pans, then line bottoms with parchment. In a large bowl, whisk flour, cocoa powder, sugar, baking soda, and salt. Add eggs, buttermilk, oil, and vanilla. Beat on medium speed for 2 minutes until smooth. Stir in hot coffee - the batter will be thin.

Divide batter evenly between pans. Bake 30-35 minutes until a toothpick inserted in center comes out with a few moist crumbs. Cool in pans 10 minutes, then turn out onto wire racks to cool completely.

Drain cherries, reserving 1 cup juice. Combine juice, sugar, and cornstarch in a saucepan. Cook over medium heat, whisking constantly, until mixture thickens and bubbles, about 3-4 minutes. Remove from heat and stir in kirsch and cherries. Cool to room temperature.

Beat cold heavy cream with powdered sugar and vanilla on medium-high speed until stiff peaks form - about 3-4 minutes. Do not overbeat or it will become grainy.

Split each cake layer horizontally with a serrated knife to create 4 thin layers total. Place one layer on a cake stand and brush generously with kirsch. Spread with one-third of the cherry filling, then one-third of the whipped cream. Repeat with remaining layers, finishing with whipped cream on top.

Cover sides of cake with remaining whipped cream. Press chocolate shavings onto sides. Pipe rosettes of whipped cream around top edge and crown each with a fresh cherry. Refrigerate at least 1 hour before slicing - this sets the cream and makes clean cuts possible.