Preheat the oven to 160° C fan.
Butter the baking tin & add breadcrumbs; discard any breadcrumbs not fixed.
Prepare the orange zest.
With you handheld electric mixer whisk the butter, the sugar, the eggs & add a pinch of salt - until creamy.
Mix the flour & the baking powder.
Add the butter-sugar-egg mess & whisk until well combined.
Add the orange zest, the marmalade & the orange liqueur & whisk.
Finally fold in the chocolate flakes w/ a spoon.
Pour the mess into the baking tin & let it bake in the preheated oven for about 45 min. Make the famous test w/ the wooden pin ...
Let the cake rest in the baking tin for about 15 min. Afterwards let the cake tumble out & let it cool down completely.
Melt the dark chocolate in a bain-marie & pour - spoon by spoon - all over the cake.