Beat the egg whites into hard snow with a pinch of salt and add the sugar gradually at the end of beating. Separately, mix and stir together the flour, walnuts, baking powder. Gradually add the dry ingredients to the egg whites and stir gently, while adding the vanilla last.
Finally, add the soft butter and beat well again. Transfer the mixture into a rectangular tray, covered with lightly greased baking paper, the resulting layer should not be too thick. Bake the layer at 356°F (180 °C) until tender - about 20-25 minutes, but it depends on the oven.
For the glaze, beat the egg yolks well with powdered sugar, vanilla and alcohol to form a smooth cream. Pour the cream over the hot layer, which needs to spread out smoothly by itself. Optionally, you can top the cooled layer with the cream and bake it for 5 minutes at 176°F (80 °C) to dry on top.
Once the cake is completely cool, cut it into rectangles and serve it.