"day and night"

Grind butter, 5 egg yolks and sugar well into a foam-like mass. Then add milk, flour mixed with baking powder and strong foam of whipped egg whites in parts. Grease a large baking sheet with oil, sprinkle with flour and pour 1/2 of the cooked mass into one half of it. Add chocolate or cocoa to the remaining mass and pour the dark mass onto the second half of the tray. Place a partition of cardboard wrapped in parchment between the white and brown mass. Glue the finished pastries (white and dark part) together with a fruit povidl and cut into bricks.