Marinate the raisins in the rum.
Grate the chocolate. Melt the chocolate over a hot water bath and let cool.
Preheat the oven to 180°C (approximately 350°F).
Form a 5 cm high aluminum foil edge on around a baking sheet. Grease the baking sheet.
Separate the eggs. Beat the butter until fluffy. Add the egg yolks, sugar and vanilla sugar. Beat until creamy.
Stir in the melted chocolate and walnuts. Sift the cocoa powder and flour into the mixture and mix well. Stir in the rum raisins. Whip the egg whites until stiff and fold into the batter. Pour the batter onto the baking sheet and smooth. Bake for about 40 minutes.
Remove from the oven and cool on a wire rack.
Chop the chocolate and melt over a hot water bath.
Spread the melted chocolate over the brownies and sprinkle with chocolate shavings.
Cut into squares and serve.