Beat egg white, sugar, vanilla sugar and rum aroma (best of all, let everything trickle in slowly) with the whisk of the hand mixer on the highest setting so stiffly that a knife cut remains visible. Now fold in the ground walnuts.
In a large non-stick pan, reduce the mixture by half over a medium heat, stirring constantly. Place the whipped cream on a large plate to cool. Cut off small portions from the cooled mass with a teaspoon and shape into croissants. Brush these with egg white and press into the chopped walnuts.
Bake on baking paper in a preheated oven for about 25 minutes. Hot air 120 ° C top / bottom heating 140 ° C. Then remove from the baking sheet with the baking paper and let cool on a wire rack.
Melt the chocolate with oil, dip the corners of the croissants and let them set again on the baking paper. Delicious and something for real walnut fans.