A rich and moist chocolate cake layered with a luscious chocolate filling and topped with a smooth chocolate frosting.
Preheat your oven to 350°F (175°C) and prepare two 8-inch round cake pans by greasing and lightly flouring them.
Ensure the pans are evenly coated with flour to prevent sticking.
In a small bowl, mix the cocoa powder with boiling water to form a smooth paste.
Use a whisk to ensure there are no lumps in the paste.
In a saucepan, heat the milk and butter until the butter melts, then remove from heat.
Stir occasionally to prevent the milk from scorching.
Combine the cocoa paste with the milk mixture and let it cool to room temperature.
Allow the mixture to cool completely to avoid cooking the eggs in the batter.
In a mixing bowl, cream together the sugar and eggs until light and fluffy, then mix in the vanilla extract.
Beat the mixture until it becomes pale and increases in volume.
Gradually add the cocoa mixture to the sugar mixture, mixing until well combined.
Add the cocoa mixture slowly to prevent splattering.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Sift the dry ingredients for a finer texture.
Gradually fold the dry ingredients into the wet mixture until just combined.
Avoid overmixing to keep the cake tender.
Divide the batter evenly between the prepared pans and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Rotate the pans halfway through baking for even cooking.
Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
Ensure the cakes are completely cool before assembling to prevent melting the filling.
Prepare the filling by combining cocoa powder, boiling water, sugar, and cornstarch in a saucepan. Cook over medium heat until thickened, then stir in salt, vanilla, and butter.
Stir constantly to avoid lumps forming in the filling.
For the frosting, melt the chocolate in a double boiler, then stir in butter, hot water, corn syrup, and vanilla until smooth.
Use a double boiler to gently melt the chocolate without burning it.
Slice each cake layer horizontally to create four layers. Place one layer on a serving plate and spread with a third of the filling. Repeat with the next two layers, then top with the final layer.
Use a serrated knife for clean and even cuts.
Frost the top and sides of the cake with the prepared frosting.
Use a spatula to create smooth or decorative patterns on the frosting.
Refrigerate the cake for 15 minutes to set the frosting, then serve.
Chilling the cake briefly helps the frosting firm up for cleaner slicing.