For the cappuccino cardinal slices, first beat the yolks and eggs until creamy, add the powdered sugar and continue beating until a very loose mixture is formed. Then carefully fold in the flour.
For the meringue, whip the egg whites until stiff and fold in the granulated sugar. Pour the stiff mixture into a piping bag.
Place baking paper on a baking tray and use the piping bag to pipe 3 individual strips of meringue. Leave gaps of just under 2 cm. Spoon the meringue into the free spaces. Bake in the oven heated to 160 °C on the middle shelf for 10-15 minutes. The sponge should be lightly browned.
For the filling, whip the whipped cream with cream stiffener, then fold in the cappuccino powder.
Let the baked sponge meringue mixture cool, then cut into 3 parts. Turn one part over, spread half of the filling. Place the second sponge cake part on top, spread the remaining filling. Finish with the last sponge cake part.
Put the cappuccino cardinal slices in the refrigerator for 1 hour.