1. Preheat oven to 350°F. Grease and flour an 8-inch square baking pan.

2. In a medium bowl, whisk together the flour and granulated sugar. In a separate bowl, beat the eggs until light and fluffy.

3. Gradually fold the egg mixture into the flour mixture until just combined. Pour the batter into the prepared pan and bake for 20-25 minutes, until a toothpick inserted in the center comes out clean.

4. Allow the cake to cool completely, then use a serrated knife to split it horizontally into 3 even layers.

5. In a small saucepan, heat the coffee over medium heat until simmering. Remove from heat and let cool slightly. Brush the coffee evenly over the cake layers.

6. In a medium saucepan, heat the heavy cream over medium heat until just simmering. Remove from heat, add the chopped chocolate, and let sit for 2-3 minutes. Whisk until the chocolate is melted and the mixture is smooth. Allow to cool until thickened slightly.

7. In a large bowl, beat the 1 cup of softened butter until light and fluffy. Gradually add the powdered sugar and vanilla, beating until well combined.

8. Place one cake layer on a serving platter or cake stand. Spread half of the chocolate ganache evenly over the top. Top with another cake layer and the remaining ganache. Top with the final cake layer.

9. Frost the top and sides of the cake with the buttercream. Refrigerate for at least 2 hours before serving.