Preheat your oven to 350°F (175°C) and prepare two 9-inch round cake pans by lining with parchment paper and greasing the sides.

Melt the dark chocolate in a microwave-safe bowl in 30-second intervals, then set aside to cool slightly.

Cream unsalted butter with granulated and light brown sugars using an electric mixer until light and fluffy, about 3-4 minutes.

Add large eggs one at a time, integrating them along with pure vanilla extract until smooth.

Incorporate the slightly cooled melted dark chocolate into the wet mixture, mixing on low speed.

Whisk together flour, cocoa powder, baking soda, baking powder, espresso powder, and salt in a separate bowl.

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

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

Divide the batter between prepared pans and bake for 30-35 minutes until a toothpick comes out clean.

Cool the cakes in their pans for 10 minutes before inverting onto wire racks to cool completely.

For the ganache, heat heavy cream until boiling and pour over chopped chocolate; let it sit before stirring in butter and vanilla.

Once cooled, layer cakes with ganache between layers and pour remaining ganache over the top.