Preheat oven to 375°F.

Using a double boiler or a heatproof bowl over a gently simmering saucepan of water, add chocolate and butter. Heat, stirring occasionally, until fully melted.

Remove bowl from heat and add sugar; whisk until just combined.

Add eggs and vanilla extract; whisk until just combined.

Add cocoa powder and whisk until just combined.

Pour batter into prepared pan and bake for 25 minutes. Set cake aside to cool completely (~1 hour), but do not release springform pan.

Using a small bowl, whisk together cocoa powder, hot water and bourbon whiskey; set bowl aside.

Using a double boiler or a heatproof bowl over a gently simmering saucepan of water, add chocolate. Heat, stirring occasionally, until fully melted. Remove chocolate from heat and stir in the cocoa powder mixture. Set aside and let cool for 5 minutes.

Gently stir ⅓ of the whipped cream into the chocolate mixture. Using a spatula, fold in the remaining whipped cream.

Using an offset spatula, spread mixture evenly into the pan (on top of cake layer). Tap pan firmly on counter several times to remove any air bubbles. Place pan in refrigerator for at least 30 minutes.

Place the chopped chocolate in a large heatproof bowl.

Once boiling, pour the cream mixture into the bowl with the chocolate; let stand for 5 minutes. Stir until smooth.

Place 1 cup of ganache in refrigerator for at least 1 hour. Let remaining ganache cool to room temperature.

Transfer the chilled ganache into a piping bag fitted with a small star tip. Pipe stars around outer edge of cake.

Refrigerate cake for at least 3 hours before slicing and serving.

Store any leftover cake in the refrigerator.