Start by preheating the oven to 350°F (175°C). Grease and lightly flour two 9-inch round cake pans.

In a small saucepan over low heat, melt 4 ounces of Swiss chocolate, stirring until smooth. Set it aside to cool slightly.

In a large mixing bowl, beat together the softened butter and sugar until creamy and smooth. This step helps achieve a tender texture in the cake.

Add the eggs one at a time, beating well after each addition. Then add the vanilla extract, which will enhance the cake’s sweetness and balance the chocolate flavor.

In a separate bowl, sift together the flour, baking powder, and salt.

Gradually add the dry ingredients to the butter mixture, alternating with milk. Start and end with the dry ingredients to keep the batter smooth.

Gently fold the melted chocolate into the batter, stirring until well combined. Avoid over-mixing to keep the cake light and fluffy.

Divide the batter evenly between the prepared pans. Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer them to a cooling rack.

While the cake cools, make the frosting. In a mixing bowl, beat together the melted chocolate and softened butter until smooth. Gradually add the powdered sugar, milk, and vanilla, beating until creamy and spreadable.

Once the cake layers are completely cooled, frost the top of one layer, stack the other layer on top, and frost the entire cake. Smooth the frosting with a spatula for an even finish.