Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans, lining the bottoms with parchment paper.

In a microwave-safe bowl, melt the dark chocolate by microwaving it in 30-second intervals, stirring until smooth.

Cream the unsalted butter, granulated sugar, and brown sugar together in a mixing bowl until light and fluffy.

Incorporate the large eggs one at a time into the butter mixture, followed by the pure vanilla extract, mixing well.

Mix the melted chocolate into the wet ingredients on low speed until combined.

In a separate bowl, whisk the flour, cocoa powder, baking soda, baking powder, espresso powder, and salt together, then alternate mixing with buttermilk into the wet ingredients.

Gently fold in the semi-sweet chocolate chips using a spatula.

Divide the batter evenly between the prepared cake pans and bake for 30-35 minutes or until a toothpick comes out with a few moist crumbs.

Let the cakes cool in their pans for about 10 minutes before transferring to wire racks to cool completely.

To make the ganache, heat heavy cream in a saucepan, pour over chopped dark chocolate, let sit, then stir until smooth. Mix in butter, vanilla, and corn syrup.

Once cooled, assemble the cake by layering ganache between the cake layers and pouring the remaining ganache over the top.

Slice and serve the cake, optionally pairing with vanilla ice cream or fresh berries.