Preheat oven to 350°F. Grease three 6-inch cake pans and line with parchment paper.

In a small bowl, whisk flour, baking powder, baking soda, and salt.

In a large mixing bowl, cream butter and sugar with an electric mixer until light and fluffy.

Beat in eggs one at a time, then add vanilla extract.

In a measuring cup, combine brewed coffee and buttermilk.

Add flour mixture and coffee mixture alternately into the butter mixture, starting and ending with the flour. Mix until combined.

Divide batter evenly into cake pans. Bake 20–25 minutes or until a toothpick comes out with fine crumbs. Cool in pans for 10 minutes, then transfer to a wire rack to cool completely.

For the buttercream, beat butter until pale and creamy. Add powdered sugar, vanilla, and espresso. Beat until smooth, adjusting consistency as needed.

Place the first cake layer on a serving plate. Spread ⅓ to ½ cup frosting evenly. Repeat with the second layer. Place the third layer bottom side up. Apply a thin crumb coat of frosting over the entire cake and chill for 20–30 minutes.

Frost the sides and top with remaining buttercream, reserving ¾ cup for piping decorations.

For the ganache, heat cream and espresso until steaming. Pour over chocolate chips, let sit for 2 minutes, then whisk until smooth. Cool close to room temperature.

Spoon ganache slowly over the top edge of the cake, letting it drip down the sides. Pipe a border with reserved frosting. Dust with cocoa powder or garnish with coffee beans if desired.