Start by preheating your oven to 350°F (175°C). Grease and flour your two 8-inch round cake pans or line them with parchment paper to ensure the cakes don’t stick.

In a large mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. This is crucial for ensuring that all the dry ingredients are evenly distributed throughout the batter.

In a separate bowl, beat together the eggs, granulated sugar, brown sugar, milk, vegetable oil, and vanilla extract. Use an electric mixer or a hand whisk until smooth and combined.

Gradually add the dry ingredients into the wet mixture. Mix on low speed to avoid splattering, then increase to medium speed until smooth. The batter will be thick at this point, but don’t worry—it will come together perfectly.

Carefully pour the boiling water into the batter and mix it in. The batter will be thin, but that’s exactly what you want—it helps the cake bake evenly and keeps it moist.

Divide the batter equally between the two prepared pans. Bake in the preheated oven for about 30-35 minutes, or until a toothpick inserted into the center comes out clean. Be careful not to overbake; a moist cake is the key to a Swiss chocolate cake that melts in your mouth.

Let the cakes cool in their pans for about 10 minutes, then transfer them onto a cooling rack to cool completely. This prevents the frosting from melting when you apply it to warm cake layers.

While the cakes are cooling, prepare the frosting. Beat the softened butter in a large mixing bowl until light and fluffy.

Gradually add the powdered sugar, cocoa powder, and a pinch of salt, alternating with the milk, until you achieve a smooth, creamy frosting. You can adjust the consistency by adding more milk if needed.

Once the cakes are fully cooled, spread a generous amount of frosting on top of one layer. Place the second layer on top, then spread frosting over the top and sides of the entire cake.