For the yeast dough
Cream the yeast with the milk and 1 tbsp sugar, then put into a mixing bowl with the rest of the dough ingredients and knead to a smooth dough, using the dough hook of an electric mixer.
Cover and put in a warm place to rise for about 30 minutes.
For the topping
Put half the blancmange powder into a pan with the milk and 75 g sugar, boil until it thickens and then chill.
Separate the eggs. Whisk the egg whites stiffly with the salt.
Mix the egg yolks with the rest of the sugar and vanilla sugar until foamy.
Add the quark, lemon rind and juice, raisins, ground almonds, blancmange and the rest of the blancmange powder and mix thoroughly.
Fold the beaten egg whites into the quark mixture.
Grease a baking tray. Knead the dough and roll out on the baking tray.
Spread the quark mixture on the dough and bake in a preheated oven (175°C; middle shelf) for about 50 minutes.
Take out and cool slightly.
For the icing
Melt the nougat in a bain-marie, spread on the cake and leave to cool completely.
Cut into squares to serve.