Preheat the oven to 180°C. Grease a shallow baking pan with butter and line with baking paper. Sift the flour, baking powder and cocoa powder into a bowl and add 225 g butter, the brown sugar and the eggs.
Mix the cappuccino powder with 2 tablespoons of hot water and add it as well.
Mix everything together until smooth, pour into the pan and smooth the surface. Bake in a hot oven for about 35-40 minutes until the dough has risen. Then let cool in the pan for 10 minutes, turn out onto a cooling rack and peel off the baking paper.
Let cool completely. For the glaze, put the white chocolate, 55 g butter and milk in a bowl and set it on a pan of simmering water. Melt the chocolate while stirring. Remove the bowl from the pot and sift in the powdered sugar. Stir until smooth, spread on the dough and dust with cocoa powder.
Then cut into rectangles. Tip: When melting, make sure that the bottom of the bowl does not touch the boiling water so that the chocolate does not become too hot and thus unusable.