Preheat your oven to 350°F (175°C) and prepare your baking pan by greasing it and lining the bottom with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, dark cocoa powder, baking soda, baking powder, and salt until well combined.

In a separate bowl, combine the large eggs and granulated sugar, then beat them together until light and fluffy.

Gradually combine the wet mixture with the dry ingredients, stirring gently until just combined. Pour in the hot brewed coffee.

Pour the batter into the prepared baking pan and bake for 35-40 minutes, or until a toothpick comes out clean.

Once baked, let the cake cool in the pan for about 10-15 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat the softened unsalted butter until creamy, then gradually add the powdered sugar.

Dissolve the instant espresso powder in the heavy cream and blend into the creamed butter until smooth.

Frost the cooled Dark Chocolate Cake generously with the espresso buttercream.

Slice and serve the cake, optionally with dark roast coffee or vanilla ice cream.