Method:

• Preheat your oven to 350°F (175°C). This ensures that your cakes will bake evenly.
• Grease and flour your two 9-inch round cake pans. This will help the cakes come out smoothly after baking.
• In a large mixing bowl, combine the granulated sugar, light brown sugar, all-purpose flour, sifted cocoa powder, baking soda, baking powder, and salt. Whisk them together until well blended.
• In another bowl, whisk together the large eggs, egg yolks, whole milk, sour cream, vegetable oil, and vanilla extract. Mix until the wet ingredients are well combined.
• Gradually add the wet ingredients into the dry mixture, mixing well until there are no lumps. The batter will be quite thick at this point.
• Slowly stir in the hot water until fully incorporated. This will thin out the batter and create a moist cake.
• Gently fold in the chocolate chips until evenly distributed throughout the batter.
• Divide the batter evenly between the prepared cake pans. Bake in the preheated oven for 30 to 35 minutes, or until a toothpick inserted in the center comes out clean.
• Once baked, let the cakes cool in the pans for about 10 minutes before transferring them to a cooling rack to cool completely.
• In a large bowl, beat the very soft unsalted butter with an electric mixer until creamy. Gradually add the sifted confectioners' sugar and cocoa powder, mixing until combined. Add the vanilla extract, salt, and heavy cream, beating until the desired consistency is reached.
• Once the cakes are completely cool, place one layer on a serving plate. Spread a generous amount of frosting on top, then place the second layer on top. Frost the top and sides of the cake generously.
• Drizzle hot fudge sauce over the top of the frosted cake and sprinkle with chocolate shavings and additional chocolate chips for a stunning finish.