Melt butter with milk at 60–65°C.

Whisk eggs and sugar vigorously until foamy.

Whip until the mixture turns ivory-colored and forms ribbons.

Sift flour and cocoa powder into the batter and mix lightly by hand.

Combine the melted butter and milk mixture with the batter.

Pour batter onto a flat baking tray and smooth out bubbles.

Bake at 180°C/165°C for 15 minutes.

Cover the baked sponge with parchment paper and let cool.

Heat cream and mix with chopped chocolate until smooth.

Spread whipped cream onto the cooled sponge and roll tightly.

Freeze the rolled cake, then coat with ganache and decorate with chocolate shavings.