Preheat oven to 325°F (170°C). Line bottom of 2 (8-inch) round cake pans with parchment paper.

In a large bowl, whisk together ¼ cup (60 grams) boiling water and cocoa. Whisk in ½ cup (100 grams) sugar until dissolved. Let cool slightly, about 3 minutes. Whisk in melted chocolate, egg yolks, oil, and vanilla until well combined.

In a medium bowl, sift together flour, salt, baking powder, and baking soda. Gradually whisk flour mixture into chocolate mixture. (Mixture will be thick.)

In the bowl of a stand mixer fitted with the whisk attachment, beat egg whites at medium-high speed until foamy. Reduce mixer speed to medium-low, and add remaining ⅓ cup (67 grams) sugar in a slow, steady stream. Increase mixer speed to medium-high, and beat until medium-soft peaks form.

Fold one-third of egg white mixture into chocolate mixture. (This will thin out the batter.) Carefully fold in remaining egg white mixture in two additions. Divide batter between prepared pans (about 402 grams each). Run a knife through batter to help release any large air bubbles.

Bake until fragrant and top is firm to the touch when gently pressed, about 25 minutes. Let cool in pans on wire racks for 10 minutes. Run a small offset spatula or thin knife between cake layers and sides of pans. Remove from pans, and let cool completely on wire racks.

Place 1 cooled cake layer, upside down, on a cake plate. Brush half of Black Cherry Kirschwasser Simple Syrup (about ½ cup or 78 grams) onto cake layer.

Place 1½ cups (210 grams) Whipped Frosting in a pastry bag, and cut a 1-inch opening in tip. Pipe a thick border around edge of cake layer. Spoon Cherry Filling into center of cake layer, and gently spread until flat and reaches frosting border. Place remaining cake layer, upside down, on top. Brush remaining Black Cherry Kirschwasser Simple Syrup onto cake layer. Using frosting in pastry bag, fill any holes between cake layers, if needed; scrape any remaining frosting in bag back into bowl. Spread a thin coat of frosting on top and sides of cake to create a crumb coat. Freeze cake for 20 minutes, and refrigerate frosting.

Spread remaining Whipped Frosting on top and sides of cake as desired. Cover and refrigerate for at least 4 hours before serving. Just before serving, add Chocolate Curls to top of cake with tweezers or by sliding a wooden pick into center of curl to lift. Cover and refrigerate for up to 3 days.

In a small saucepan, stir together sugar and 3 tablespoons (45 grams) water. Cook over medium heat, stirring occasionally, until sugar dissolves. Pour into a heatproof bowl. Stir in kirschwasser. See note.

In a medium saucepan, whisk together sugar, cornstarch, and salt. Stir in 1¾ cups (254 or 306 grams) cherries, kirschwasser, and lemon juice. Bring to a boil over medium- high heat, stirring frequently and mashing cherries. Reduce heat to medium; cook, stirring frequently, until mixture is reduced to about 1¼ cups, 5 to 7 minutes. Stir in remaining 1 cup (145 or 175 grams) cherries, and transfer to a heatproof bowl. Let cool completely before using.

In the bowl of a stand mixer fitted with the paddle attachment, beat cream cheese at medium speed until smooth, about 1 minute. Add sugar, and beat at medium-low speed until sugar dissolves and mixture is smooth, stopping to scrape sides of bowl. With mixer on medium-low speed, add cold cream in a slow, steady stream. Once all cream has been added, thoroughly scrape sides of bowl.

Switch to the whisk attachment. Beat at low speed, and slowly increase mixer speed to medium as mixture thickens, beating until thick and stiff peaks form. Beat in vanilla.

In a small microwave-safe bowl, heat chocolate on high in 30-second intervals, stirring between each, until melted and smooth. Stir in oil. Spread chocolate mixture into a thin, even layer on bottom of an 18x13- inch baking sheet, leaving about a 2-inch border on all sides. Freeze until hardened enough to curl when scraped, 4 to 5 minutes, checking every minute and testing corner with a small metal spatula.

Working along one long side and using a small metal spatula, scrape chocolate into curls. (If chocolate gets too soft, freeze for about 1 minute; if chocolate is too cold and breaking when scraped, let stand at room temperature for about 1 minute.) Freeze curls until ready to use.