01 -
Preheat oven to 350°F and position rack in the center. Grease two 9-inch round cake pans, line bottoms with parchment paper, and dust sides with cocoa powder.
02 -
In a large bowl, whisk together flour, cocoa powder, sugar, baking powder, baking soda, and salt. Break up cocoa lumps for even batter texture.
03 -
In a medium bowl, whisk eggs until blended and lighter in color. Add milk, vegetable oil, and vanilla extract, mixing until smooth.
04 -
Pour wet ingredients into dry mixture and whisk until no dry streaks remain. Slowly add hot coffee while mixing until batter is smooth and thin. Scrape bowl to combine evenly.
05 -
Divide batter evenly between pans, smoothing tops. Bake 30 to 35 minutes or until toothpick inserted comes out with moist crumbs. Cool in pans 10 minutes, then transfer to wire racks to cool completely.
06 -
Place chocolate chips in a heatproof bowl. In a small saucepan, heat heavy cream until simmering at edges. Pour hot cream over chocolate and let rest 2 to 3 minutes. Add butter if using and whisk until smooth and glossy.
07 -
Level cake layers if domed. Place one layer on serving plate, spread ganache on top as filling. Add second layer, pour remaining ganache over top, spreading toward edges. Allow ganache to thicken 20 to 30 minutes before slicing.