Preheat the oven to 180°C (circulating air). Melt the butter and chocolate in a pot, piece by piece. When the chocolate-butter mixture is shiny and smooth, put aside. In a baking bowl, beat the eggs with sugar and vanilla sugar until frothy.
Slowly add flour, then add salt and mix everything well with a mixer.
Using a dough scraper, add the liquid chocolate to the flour-egg-sugar mixture and fold in well. Then mix briefly with a mixer. Add brittle and rum and fold in well.
Line a baking tray with baking paper. Spread the whole mixture on the baking tray and bake at 180 degrees for about 18 - 20 minutes. It is important that the brownies are not baked through, so that they remain nice and chocolaty.
Cut the cooled cake into even pieces and serve. Serve with Häagen-Dazs Vanilla Ice Cream.