Sift the flour and pour it into a suitable bowl, while also adding the other dry ingredients for the dough to it. Stir well with a spoon. Stir the yoghurt and add it to the flour, along with the butter and walnuts. Mix everything very well.
Pour the mixture into an oven dish with a nonstick coating, which you've smeared ahead of time with butter. Bake the cake about 30 min. at 356°F (180 °C).
For the glaze:
Pour all the ingredients for the glaze in a small container. Place it into another container with water on the stove and melt in a water bath on low heat, while stirring to obtain a smooth glaze. Pour this glaze over the cake.
For the decoration:
Melt several white chocolate blocks in a water bath. Pour the melted chocolate in a funnel made from baking paper. Cut just a little bit off the top and spray out flowers over the glaze. Cut the cake into squares.