01 -
Beat softened butter with granulated sugar and vanilla sugar until light and fluffy to incorporate air for a tender crumb.
02 -
Add eggs one at a time, mixing well after each addition to ensure full integration.
03 -
Sift together flour and baking powder to ensure even distribution.
04 -
Slowly fold dry mixture into the batter, followed by milk, mixing minimally to avoid gluten development that would make the cake dense.
05 -
Transfer half of the light batter into a greased loaf pan.
06 -
Add cocoa powder and additional sugar to the remaining batter, stir gently until evenly combined.
07 -
Pour chocolate batter over the light batter in the pan. Use a fork to swirl both layers together, creating a marbled pattern without overmixing.
08 -
Bake in a preheated oven at 350°F (175°C) for 50-60 minutes, checking doneness with a wooden skewer starting at 50 minutes to avoid overbaking.
09 -
Allow cake to cool before applying optional melted chocolate glaze or dusting with powdered sugar. Garnish with chocolate shavings if desired.