Prepare the Cherry Filling:
In a small saucepan, combine cherries, sugar, cornstarch, and lemon juice. Cook over medium heat until the mixture thickens, around 5-7 minutes. Set aside to cool.
Make the Cupcake Batter:
Preheat your oven to 350°F (175°C) and line a cupcake pan with paper liners.
In a mixing bowl, combine flour, baking powder, baking soda, salt, sugar, and cocoa powder. Mix well.
Add egg, buttermilk, vegetable oil, and vanilla extract. Beat with an electric mixer on medium speed until combined.
Gradually stir in the boiling water until the batter is smooth and well-combined.
Bake the Cupcakes:
Fill each cupcake liner about 2/3 full with the batter. Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean. Allow cupcakes to cool completely on a wire rack.
Assemble the Cupcakes:
Once the cupcakes are cool, make the whipped cream by beating the heavy cream, powdered sugar, and vanilla extract until soft peaks form.
Carefully core each cupcake and fill it with the cherry mixture. Top with whipped cream and garnish with chocolate shavings or a dusting of cocoa powder.