Preheat your oven to 180°C (350°F) and prepare an 8-inch cake pan by greasing it with butter and dusting it with breadcrumbs.
Use a small saucepan to melt the butter, then set it aside to cool.
Strain the flour and set it aside as well.
Combine eggs and sugar in a large mixing bowl.
Mix until you get a pale-colored mixture, then add the cocoa powder and vanilla sugar.
Pour the cooled, melted butter and mix.
Add the flour and use a spatula to fold it with the rest of the kladdkaka batter.
Pour the Swedish sticky chocolate cake batter into the prepared pan.
Use an angled spatula to even the top.
Place the kladdkaka pan in the lower part of the oven for 12 to 15 minutes.
Remove from the oven and let cool for about 10 minutes.
Your traditional kladdkaka is now ready for serving!