Preheat your oven to 350°F (175°C) and prep two 9-inch round cake pans by lining them with parchment paper and greasing them with unsalted butter.

In a microwave-safe bowl, melt the chopped dark chocolate gently, then allow to cool slightly.

Cream room temperature unsalted butter with granulated sugar and light brown sugar until light and fluffy.

Incorporate large eggs one at a time, beating well after each addition, then stir in the pure vanilla extract.

Add the cooled melted chocolate to the creamed mixture and blend on low speed until combined.

In another bowl, whisk together all-purpose flour, Dutch-processed cocoa powder, baking soda, baking powder, espresso powder, and salt.

Gradually mix the dry ingredients into the wet mixture, alternating with buttermilk.

Fold in semi-sweet chocolate chips, ensuring even distribution.

Divide batter between prepared pans and bake for 30-35 minutes; check doneness with a toothpick.

Cool the cakes in pans for 10 minutes before transferring to a wire rack to cool completely.

Heat heavy cream until simmering, then mix it with chopped dark chocolate to form ganache; stir in butter.

Assemble the cake by layering with ganache between the cake layers and drizzling remaining ganache on top.