Preheat the oven to 350℉ and line a 9X13 inch pan with parchment paper. Set aside.
Sift the dry ingredients, including flour, sugar, espresso powder, baking soda, and salt.
2 cups All-purpose flour, 2 cups Sugar, 1 teaspoon Espresso powder, 1 teaspoon Baking soda, ½ teaspoon Salt
Mix the water, Cocoa powder, and butter in a saucepan, boil, and stir constantly.
1 cup Butter, ⅓ cup Cocoa powder, 1 cup water
Add in the eggs, buttermilk, and vanilla extract.
2 Eggs, ½ cup Buttermilk, 1 tablespoon Vanilla extract
Bake the cake and let it cool down in the pan for 10 minutes, then transfer it to the cooling rack.
How To Make The Fudge Topping
In a saucepan, combine the butter, cocoa powder, and buttermilk and bring it to a boil.
¼ cup Butter, 3 tablespoon Cocoa powder, ¼ cup Buttermilk
Remove it from the heat and add the powdered sugar and vanilla extract. mix well. If you desire to add nuts, add them now and mix.
2¼ cups Powdered sugar, 1 teaspoon Vanilla extract, ½ cup Pecans
Poke the Hot Fudge Cake with a skewer to make the frosting penetrate the cake batter. Pour the hot mixture over the cake and let the icing set for one hour at least. Cut it into squares and serve warm.